1. [The following rules apply when] there is a window between two courtyards: If the window is four handbreadths by four handbreadths¹As reflected by the Rambam's ruling, Hilchot Tum'at Meit 7:1, this is the minimum size that a human being can squeeze through. For this reason, it is necessary that it be at least four handbreadths on each side; a total area of 16 square handbreadths is not sufficient (Shulchan Aruch HaRav 372:5; Mishnah Berurah 372:30). (See also the following halachah.) or larger and it is within ten handbreadths of the ground - whether it is [almost] entirely above ten handbreadths and only a [small] portion is within ten handbreadths, or it is [almost] entirely within ten handbreadths and only a [small] portion is above ten handbreadths - [an option is granted to] the inhabitants of the courtyards.²Since the window is of sufficient size and it is close to the ground, the inhabitants of the courtyards are granted the option of considering it an entrance. If this option is taken, it causes the two courtyards to be considered a single entity.

If they desire to join in a single eruv, they may. This causes [the entire area] to be considered a single courtyard, and carrying is permitted from one [courtyard] to the other.³The Mishnah Berurah 372:27 emphasizes that this ruling applies only when the courtyards did not join together in a shituf to permit carrying in the entire lane. If they desire, they may make two eruvim, each for [the inhabitants of their respective courtyards]. [It is then forbidden] to carry from one courtyard to the other.]

If the windows are smaller than four [handbreadths by four handbreadths] or the entire window is above ten handbreadths from the ground,⁴The window cannot be considered to be an entrance. Hence, the courtyards are considered to be separate. they may make two eruvim, each for [the inhabitants of the respective courtyard].

2. When does the above apply? To a window between two courtyards. When, by contrast, the window lies between two houses,⁵This refers to an instance when an eruv was not established in the courtyard. Were that the case, it would be possible to transfer articles from house to house through the window, even without a separate eruv. [they are permitted to make an eruv] even if the window is above ten handbreadths from the ground.⁶Eruvin 76b explains that a house is considered as if it is full, and thus it is as if there were less than ten handbreadths between the window and the ground.

Similarly, when there is a window between a house and a loft, if the inhabitants desire to establish a single eruv they may, even if there is not a ladder [leading to the window], provided [the window] is four [handbreadths] by four [handbreadths]. If the window is round and it can circumscribe a square that is four [handbreadths] by four [handbreadths], it is considered as if it were square.

3. When there is a wall or a mound of hay that is less than ten handbreadths high⁷A divider that is less than ten handbreadths high is not significant. Therefore, the entire area is considered to be a single domain, and all the inhabitants must join in one eruv. between two courtyards, they must make a single eruv and may not make two eruvim. If [the wall or the mound] is ten or more handbreadths high, they must make two eruvim, each for the respective courtyard.

If there is a ladder⁸The Shulchan Aruch (Orach Chayim 372:8) states that the ladder must be at least four handbreadths wide and have four rungs. The commentaries question why the Rambam does not include these restrictions. on either side of the wall,⁹How close the ladders must be to each other is explained in the following halachah. it is considered to be an entrance, and if they desire, they may establish a single eruv. Even if the ladder is standing upright, next to the wall, and it is impossible to ascend it without moving its lower portion away from the wall, it permits [them to participate in a single eruv]. [Moreover,] even if the top of the ladder does not reach the top of the wall, if there are less than three handbreadths between them,¹⁰Based on the principle of l'vud, when there is a distance of less than three handbreadths between two entities, it is considered as though they were adjacent. it permits them to participate in a single eruv if they desire.

4. If the wall is four [handbreadths] wide and a ladder is positioned on either side of the wall, they may make a single eruv, if they desire.¹¹Since the wall is more than four handbreadths wide, it is possible to walk from one ladder to the other ladder on the wall. If the wall is not four [handbreadths] wide, and there are less than three handbreadths between the [two] ladders, they may make a single eruv.¹²Based on the principle of l'vud, it is considered as though the ladders were adjacent. If there are more than three handbreadths between [the ladders], they must make two eruvim.¹³Because the ladders are distant from each other, the two courtyards are considered to be separate entities.

5. [The following rules apply when] one builds a bench¹⁴Our translation is based on Eruvin 77b, the apparent source for the halachah. above a bench at the side of a wall [separating two courtyards]: If the lower bench is four handbreadths [high], [we consider it as if the height of the wall] were reduced.¹⁵Since one can climb over the wall easily by ascending onto the bench, the wall is no longer considered an absolute division between the courtyards, and it is possible to establish an eruv, joining both courtyards.

This is the conception of the Rambam. The Shulchan Aruch (Orach Chayim 372:9,11) follows the view of Rabbenu Asher which is more stringent and which maintains that a bench does not create the option of fusing the two courtyards into a single entity. The only leniency which is permitted is that the inhabitants of the courtyard where the bench is located may use the top of the wall. If the lower [bench] is not four handbreadths [high], but there are less than three handbreadths between it and the upper [bench], [we consider it as if the height of the wall] were reduced.

[In such situations,] if [the inhabitants of the courtyards] desire, they may make a single eruv. Similar [principles apply] regarding wooden steps placed close to a wall.

6. [The following rules apply when] there is a high wall separating two courtyards, and a projection¹⁶The projection must be at least four handbreadths by four handbreadths (Shulchan Aruch, Orach Chayim 372:12). protrudes from the middle of the wall: If less than ten handbreadths remain from the projection to the top of the wall, one may lean a ladder in front of the projection,¹⁷In this way, the inhabitants can easily cross over the wall by climbing from the ground to the projection and from the projection to the top of the wall. and [this grants the inhabitants] the option of making a single eruv. If, however, one stands the ladder [against the wall] at the side of the projection, [we do] not [consider it as if the height of the wall were] reduced.¹⁸When the ladder is leaning on the projection, they are considered to be a single unit. When, by contrast, the ladder is leaning against the wall, even if it is in within three handbreadths of the projection, they are not considered to be a single unit (Shulchan Aruch HaRav 372:15; Mishnah Berurah 372:98-99).

If the wall is nineteen handbreadths high, [it is sufficient] to have a projection protrude for the inhabitants to have the option of making a single eruv. For there are less than ten handbreadths from the earth to the projection, and less than ten handbreadths from the projection to the top of the wall.¹⁹Thus, they can climb over the wall easily in this fashion.

Were the wall to be twenty handbreadths high, two projections are required for the inhabitants to have the option of establishing a single eruv. [Moreover, the projections] may not be parallel to each other:²⁰In this way, a ladder can be extended from one projection to another. Also, these projections must lie within ten handbreadths of each other. Thus, the people can climb from the earth to the first projection, from the first projection to the second, and from the second to the top of the wall.

In this instance as well, the Shulchan Aruch (Orach Chayim 372:12) follows the view of Rabbenu Asher which is more stringent and which maintains that the projections do not create the option of fusing the two courtyards into a single entity. The only leniency which is permitted is that the inhabitants of the courtyard where the projections are located may use the top of the wall. [In this way,] there will be less than ten handbreadths between the lower projection and the ground, and less than ten handbreadths between the upper projection and the top of the wall.

7. If a date palm is chopped down and inclined from the earth to the top of a wall, the inhabitants have the option of establishing a single eruv.²¹I.e., the date palm is considered to be a ladder, enabling people to climb across the wall. It is not necessary for them to make it a permanent part of the structure. Similarly, the [very] weight of a ladder²²The Maggid Mishneh notes that Eruvin 78a mentions a Babylonian ladder, for these ladders were large and heavy. The Maggid Mishneh explains that this concept is intimated by the Rambam's words "the [very] weight of the ladder...." These rules do not apply to a light ladder that is easily carried from place to place. causes it to be considered as having been placed permanently; it is not necessary to affix it to the structure.

If [the divider] separating two courtyards is made of straw,²³Our additions to the text are based on the commentary of the Meiri on Eruvin, loc. cit. A similar approach is also reflected in the gloss of the Maggid Mishneh on this halachah. Rashi offers a different interpretation of that Talmudic passage, and his understanding is quoted in the Shulchan Aruch (Orach Chayim 372:13). [the inhabitants] may not make a single eruv although there are ladders on either side. A person will not ascend the ladder, because nothing is supporting it.²⁴I.e., the straw divider will not support the weight of a person climbing on the ladder. If the ladders are in the center, [leaning on a firm support,] and there is straw on either side, [the inhabitants] have the option of making two eruvim.²⁵They also have the option of establishing a single eruv, if they so desire. Certain commentaries suggest amending the text of the Mishneh Torah to include this concept.

8. When there is a tree at the side of the wall, and it was used as a ladder for the wall, [the inhabitants] have the option of making a single eruv. [Although] it is forbidden to ascend a tree [on the Sabbath], since the prohibition is only a sh'vut,²⁶As the Rambam explains in Hilchot Shabbat 21:1, the Sages specified certain activities as forbidden as a safeguard to the observance of the Sabbath prohibitions. Each of the forbidden activities is referred to as a sh'vut. See also Hilchot Shabbat 21:6 which prohibits climbing trees. [this does not cause the option to be denied].²⁷For when a mitzvah is involved, we are not bound by the prohibitions in the category of sh'vut during beyn hash'mashot (Hilchot Shabbat 24:10), and that is when the eruv takes effect (Chapter 1, Halachah 21). Since the eruv was acceptable beyn hash'mashot, it is acceptable for the entire Sabbath (Shulchan Aruch HaRav 372:18).

If an asherah²⁸A tree that is worshiped. The Torah prohibits deriving any benefit from such a tree. See Exodus 34:13; Deuteronomy 7:5 and 12:3; Hilchot Avodat Kochavim 8:3. has been made to serve as a ladder for a wall, [the inhabitants do] not [have the option of] making a single eruv. For ascending [the asherah] is forbidden by the Torah, since one is forbidden to derive any benefit from it.²⁹The Shulchan Aruch (Orach Chayim 372:15) notes that Rabbenu Asher (in his gloss on Eruvin 78b) reverses the rulings and permits the establishment of a single eruv if an asherah is used as a ladder, but not if an ordinary tree is used for that purpose. The later authorities (Shulchan Aruch HaRav, loc. cit.; Mishnah Berurah 372:116) favor the Rambam's interpretation.

9. [The following rules apply when] a wall is ten handbreadths high, and [the inhabitants] desire [to tear down a portion of the wall] to reduce itsheight so that they will be able to establish a single eruv. They have the option of establishing a single eruv, provided the portion whose height they reduce is [at least] four handbreadths long.³⁰If the portion of the wall that was torn down is at least four handbreadths wide, it can be considered to be an opening.

If [the inhabitants of one of the adjoining courtyards] tear down a portion [of their side] of the wall so that it is less than ten [handbreadths high], they are granted [permission to use] the shorter portion of the wall.³¹The interpretation of the passage in Eruvin 77a, the source for this halachah, is a matter of dispute among the commentaries. Our translation is based on the Lechem Mishneh's gloss on the Mishneh Torah. The remainder of the wall that is high is divided between [the inhabitants of] both courtyards.

10. [The following rules apply when] a high wall between [two] courtyards is breached: If the breach is ten cubits [wide] or less, they [still may] establish two eruvin.³²For the breach is not large enough to nullify the importance of the entire divider, provided the entire wall has not been destroyed. They do, however, have the option of establishing a single eruv, because [the breach] can be considered to be an opening. If [the breach] is more than ten [cubits wide], their only option is to establish a single eruv; they may not establish two eruvin.³³An opening of that size causes the entire divider to be considered as having no significance. It is as if there were only one courtyard. (See Hilchot Shabbat 16:16.)

11. If the breach is less than ten [cubits wide], and one [desires to] make it more than ten cubits, it is necessary to hollow out³⁴This represents the Rambam's interpretation of Eruvin 78b. The Ra'avad and others conceive of this passage in a different light. It is their view that is cited in the Shulchan Aruch (Orach Chayim 372:14). a portion of the wall ten handbreadths high.³⁵This is sufficient, even though there is a portion of the wall that is higher than ten handbreadths. [When this is done, the only option remaining is to] establish a single eruv.

At the outset, if one desires to open a breach larger than ten [cubits] in the wall, it is necessary that the height of the breach be equivalent to that of [an ordinary] person.³⁶Our translation is based on the commentary of the Maggid Mishneh. Others explain this to mean the full height of the wall.

Making a breach of this height indicates that one desires to pass freely from one courtyard to another. If the breach is not this high, one might think that the opening was made solely for the purpose of transferring articles (Maggid Mishneh).

12. When there is a trench at least ten handbreadths deep and at least four handbreadths wide between two courtyards, it is necessary for [the inhabitants] to establish two eruvin.³⁷For a trench of this size is not easy to cross and hence is considered to be a divider, and each of the courtyards a distinct entity. (See Hilchot Shabbat 14:23.) If its dimensions are less than this, [the inhabitants] must establish a single eruv; [they] do not [have the option of] establishing two eruvin.³⁸A trench of this size can be crossed easily. Therefore, the entire area is considered to be a single courtyard.

If the depth of the trench is reduced by [adding] earth or pebbles, [the inhabitants] must establish a single eruv; [they] do not [have the option of] establishing two eruvin.³⁹This refers to a situation in which the depth of the trench is reduced across its entire length. If one reduces the portion in one area alone, that portion is considered to be an entrance from one courtyard to the other, and the inhabitants have the option of establishing either one or two eruvin (Mishnah Berurah 372:122). For it can be assumed that the earth and the stones were intended to become a permanent part of the trench.⁴⁰Inside a dwelling, by contrast, different concepts apply. (See Hilchot Sukkah 4:13. Note, however, Hilchot Tum'at Meit 7:6.) If, by contrast, one reduced [the depth of the trench] by adding straw or hay, the reduction is not [significant] unless one intends⁴¹According to Shulchan Aruch HaRav 372:19, one must make an explicit statement, specifying one's intent. The Mishnah Berurah 372:121 cites that view, but also quotes an opinion that maintains that it is sufficient to have such thoughts in one's heart. that they become a permanent part [of the trench].

13. Similarly, if one reduces the width [of the trench] with a board or with reeds⁴²The width of the board or the reeds themselves is not significant; what is important is that they cause the width of the trench to be reduced (Maggid Mishneh). by placing them across the entire length of the trench, [the inhabitants] must establish a single eruv; [they] do not [have the option of] establishing two eruvin.

Any entity that may be carried on the Sabbath⁴³I.e., which is not forbidden to be carried, because of the prohibitions of muktzeh. - e.g., a basket or a cup - is not considered to reduce its depth, unless one affixes it to the earth [firmly], in such a manner that one must dig with a spade to dislodge it.

14. When one places a board that is [at least] four handbreadths wide across the trench, [the board is considered to be an entrance]. [Therefore, the inhabitants] may establish a single eruv. They also have the option of establishing two eruvin.

Similar [rules apply when] two balconies are positioned opposite each other [across the public domain], and a board is extended from one balcony to the other.⁴⁴Based on the rulings of the Rashba, the Maggid Mishneh states that the same rules apply if there are less than four handbreadths between the two balconies, for it is easy to step from one balcony to the other as mentioned in Halachah 12. The Maggid Mishneh allows only one eruv to be established. The Ramah (Orach Chayim 373:1) gives the people the option of establishing one or two. [The inhabitants] may establish a single eruv. They also have the option of establishing two eruvin, each one for his own balcony.

If the two balconies are on the same side [of the public domain], but are not at the same height - instead, one is higher than the other [the following rules apply]: If they are within three handbreadths of each other, they are considered to be a single balcony⁴⁵Because of the principle of l'vud. and [the inhabitants] may establish only a single eruv. If they are more than three [handbreadths] apart, they must establish two eruvin,⁴⁶They do not have the option of extending a board from one balcony to the other, because: a) as stated in Hilchot Shabbat 16:20, an entrance is not made in a corner; b) since the balconies are at different heights, a person will be afraid to walk from one to the other. each one for his own balcony.

15. [The following rule applies when] between two courtyards, there is a wall four handbreadths wide,⁴⁷If it is less than four handbreadths wide, it is a makom patur, and may be used freely by the inhabitants of both courtyards, as stated in Hilchot Shabbat 14:7. which is ten handbreadths high from one courtyard, and at ground level⁴⁸Rashi (Eruvin 77a), the Maggid Mishneh, and the Shulchan Aruch (Orach Chayim 372:6) explain that this does not mean precisely ground level, but rather less than ten handbreadths high. Similar concepts apply regarding the trench mentioned in the second clause of the halachah. at the second courtyard: The width of the wall is granted to the inhabitants of the courtyard at which it is at ground level, and it is considered to be an extension of their courtyard. [The rationale is] that since it is easily accessible to the inhabitants [of this courtyard], and more difficult to use for [the inhabitants of the other], it is granted to those for whom it is easily accessible.

Similarly, if there is a trench between the two courtyards that is ten handbreadths deep for the courtyard on one side and at ground level for the courtyard on the other side, the width of the trench is granted to the inhabitants of the courtyard at which it is at ground level. [The rationale is] that since it is easily accessible to the inhabitants [of this courtyard], and more difficult to use for [the inhabitants of the other], it is granted to those for whom it is easily accessible.

16. [The following rules apply when] there is a wall between two courtyards that is lower than the upper courtyard, but higher than the lower courtyard:⁴⁹This describes a situation in which both courtyards are situated on an incline. [During the week,] the inhabitants of the upper courtyard may make use of the breadth of the wall by lowering articles to it, and the inhabitants of the lower courtyard may make use of it by throwing articles onto it.

On the Sabbath, the inhabitants of both courtyards are forbidden to use the wall unless they establish a single eruv. If they do not establish an eruv, it is forbidden to bring articles that were left on the breadth of this wall into the homes,⁵⁰The inhabitants of both courtyards may, however, transfer articles that had been left in their courtyards to the wall as reflected by Halachot 18 and 19 (Maggid Mishneh). nor may one bring articles from the homes to the breadth of the wall.

17. [The following rules apply when there is] a ruin that is a private domain between two houses: If [the inhabitants of] both houses can use the ruin by throwing objects into it,⁵¹I.e., there is not an entrance on either side of the ruin, but the inhabitants can throw articles into the ruin through its windows. each one causes the other to be forbidden to use it [unless they establish an eruv].

If it is easy for [the inhabitants of] one [of the houses] to use [the ruin], while [the inhabitants of] the other may not throw articles into it [easily], because it is deeper than [their domain], it is granted to those who can use it [more] easily.⁵²This follows the principle stated in Halachah 15. The inhabitants of the other house may not use the ruin at all unless they establish an eruv. They may use it by throwing articles into it.

18. All the following are considered to be [parts of] a single private domain:⁵³Our Sages decreed that although a walled city is a private domain, an eruv is necessary before one may carry freely within. They, nevertheless, restricted the scope of that decree to carrying articles from the houses outside, and from the areas outside the houses to the houses. The rationale for this leniency is that one does not usually leave articles outside. Hence, the Sages did not include this possibility in their original decree (Rashi, Eruvin 89a). all the roofs of the city - despite the fact that some are high and some are low - all the courtyards, all the enclosures that were enclosed for purposes other than dwelling and are each less in area than that required to sow two se'ah,⁵⁴See Hilchot Shabbat 16:1 for more particulars. the breadths of all the walls, and all the lanes [in which one may carry because] either a post or a beam has been erected.

One may carry articles left in one [of these areas] at the commencement of the Sabbath to another without an eruv. One may not, however, transfer articles left in the homes to these areas unless an eruv is made.

19. What is implied? When an article was left in a courtyard at the commencement of the Sabbath, whether the inhabitants of the courtyards established an eruv for themselves or whether they failed to do so, it is permitted to take the article from the courtyard to the roof or to the top of the wall. Afterwards, it may be taken from the roof to another roof adjacent to it, even if [the second roof] is higher or lower than it.

From the second roof, it may be taken to another courtyard, and from the other courtyard to a third roof in a third courtyard. From this courtyard, it may be taken to a lane, and from the lane to a fourth roof. Indeed, one may carry throughout the entire city through the courtyards and roofs, through the enclosed areas and roofs, or through the courtyards and the enclosed areas, or through [any combination] of these three types of areas, provided one does not bring this article into any of the houses [in the city].⁵⁵Eruvin 91a gives several examples of how these principles were applied by the Sages. [The latter is forbidden] unless all [the inhabitants of] these different areas join together in a single eruv.

20. [Conversely,] if an article was located in a house at the beginning of the Sabbath, and it was later taken out to a courtyard,⁵⁶The rule that follows applies even when an eruv was established in this particular courtyard, and it was permitted to bring the article there from the house. it may not be taken to another courtyard, to another roof, to the top of a wall, or to an enclosed area unless the inhabitants of all the areas through which the article passes join together in a single eruv.

21. When a cistern is located between two courtyards,⁵⁷Which did not establish an eruv together. Note the accompanying diagram. it is forbidden to draw water from it on the Sabbath unless a partition ten handbreadths high has been erected⁵⁸Separating a portion of the cistern for each individual courtyard. Although there is no prohibition from the Torah against drawing water from such a cistern, the Sages forbade using the cistern, just as they forbade using other property that is jointly owned. so that everyone would be drawing water from his own property.

Where should the partition be erected? If the partition is above the water, it is necessary that at least one handbreadth of the partition descend into the water.⁵⁹A partition that is suspended in the air is not normally acceptable. In this instance, however, additional leniency is granted, because the entire concept of forbidding carrying within water is Rabbinic in origin. (See also Hilchot Shabbat 15:13.) If the partition was constructed within the water, it must project a handbreadth outside the water, so that one domain will be distinct from the other.

22. Similarly, if a beam four handbreadths wide⁶⁰This width is required so that one person will not be drawing water from his colleague's side of the cistern. Eruvin 86b states that the Sages estimated that a bucket would not travel more than four handbreadths under water. has been placed over the mouth of the cistern, one may fill [his bucket] from this side of the beam, and the other may fill [his bucket] from the other side of the beam. Although the water is not divided below [the beam], it is considered as if one portion [of the cistern] were separated from the other. This is a leniency enacted by the Sages with regard to water.

23. When a well lies in the midst of a path⁶¹The Maggid Mishneh notes that the word "path" implies a private walk and not a public thoroughfare. See Hilchot Shabbat 15:9. With this, he counters the objections of the Ra'avad, who maintains that it is necessary for the well to be surrounded by a partition ten handbreadths high in order to draw water from it. between the walls of two courtyards, [the inhabitants of] both courtyards may draw water from it; there is no necessity for them to extend projections to the well.⁶²See Hilchot Shabbat 15:14, where such projections are required. [This ruling applies] even though the well is more than four handbreadths from each of the walls. [The rationale is] that [the presence of] a colleague's [domain] does not cause a person to be forbidden to carry [when he is lifting an entity] through the air.⁶³I.e., the inhabitants are not carrying the water from the well, but lifting it up through windows that open to the path.

Some commentaries interpret the Rambam's wording as extending the application of this ruling even to an instance where there is an opening from the courtyards to the path. Other authorities (Rashba, as quoted by the Maggid Mishneh; Tur, Orach Chayim 376), by contrast, maintain that if there are entrances from the courtyards to the path, a projection is required. The difference between these two approaches is reflected in the rulings of the Shulchan Aruch and the Ramah (Orach Chayim 376:2).

24. [The following rules apply when the wall of] a small courtyard is broken down, opening [the courtyard] entirely to a large courtyard before the commencement of the Sabbath:⁶⁴If, however, the wall is broken on the Sabbath itself, the inhabitants of the smaller courtyard may continue to carry since they were permitted to do so at the commencement of the Sabbath (the Rambam's Commentary on the Mishnah, Eruvin 9:2). The inhabitants of the large courtyard may establish an eruv for themselves and they are permitted to carry, for portions of their wall still remain [standing] on each side.⁶⁵The Shulchan Aruch (Orach Chayim 374:3) states that portions of the wall of the small courtyard must jut into the large courtyard. If that is not the case, it is permitted to carry in the small courtyard as well. From the Rambam's wording and the drawings attributed to him that accompany his Commentary on the Mishnah (Eruvin 9:2), it does not appear that he considers this to be a necessity.

The inhabitants of the small courtyard, by contrast, are forbidden to remove articles from their homes to the courtyard until they establish a single eruv together with the inhabitants of the larger courtyard. [The governing principle is that] the dwellings of the larger courtyard are considered to be [part of] the smaller courtyard, while the dwellings of the smaller courtyard are not considered to be [part of] the larger courtyard.⁶⁶See also similar statements in Hilchot Tefillah 8:7 and Hilchot Kilayim 7:19.

25. When two courtyards have established a single eruv together through a shared opening or window, and that opening or window was closed on the Sabbath,⁶⁷This refers to a situation in which the window or the opening was buried under an avalanche or the like and could not be opened without violating the Sabbath laws (Rashi, Eruvin 93b). [the inhabitants of] each of the courtyards may carry within [their own courtyard].⁶⁸The Ra'avad extends the leniency even further and maintains that the inhabitants of the courtyards may also pass articles from one courtyard to the other - e.g., by passing them over the wall. His opinion is cited by the Shulchan Aruch (Orach Chayim 374:1). Since [carrying] was permitted for a portion of the Sabbath, it is permitted for the entire Sabbath.

Similarly, if [the inhabitants of] two courtyards have each established a separate eruv and the wall between them fell on the Sabbath, [the inhabitants of each courtyard] are still permitted [to carry] within their original area.⁶⁹We do not say that the entire area should now be considered a single courtyard, and since an eruv was not established before the Sabbath, carrying is forbidden. They may each take articles from their homes and carry them to the point where they could originally.

[The rationale is that] since [carrying] was permitted for a portion of the Sabbath, it is permitted for the entire Sabbath.⁷⁰When citing this law, the Shulchan Aruch (loc. cit.:2) makes a point of emphasizing that if the wall between a courtyard and a public domain or a carmelit falls on the Sabbath, carrying is no longer permitted within the courtyard. Although the number of people [within the courtyard] was increased, an increase of people on the Sabbath itself does not cause carrying to be forbidden.

[In the instance mentioned in the first clause, if after the opening or window was closed on the Sabbath,]⁷¹In this instance, as well, the Shulchan Aruch (loc. cit.:1) mentions a further leniency. If an eruv has been established for an entire year between two courtyards, the opening between them was closed during the week (and thus at the commencement of the Sabbath it was not permitted to carry from one to the other), if an opening were made on the Sabbath, it would be permitted to carry from one to the other. the window was opened inadvertently, or an entrance was made, or gentiles made [an opening] on their own volition, it is again permitted [to carry from one to the other].

Similarly, if two ships were tied to each other and an eruv was established between them, it becomes forbidden to carry from one to the other if the connection between them is severed.⁷²The Rambam's ruling is based on his interpretation of Eruvin 101b. Other authorities have different conceptions of that Talmudic passage. [This ruling applies] even if they are surrounded by a partition. If the connection was reestablished inadvertently, it is again permitted [to carry from one to the other].