In the fourth aliyah Moshe repeats the Ten Commandments that the Jewish people originally received at Mount Sinai, that we read about in parsha Yisro, in the book of Shmos.

The Ten Commandments are:

1. Believe in G-d
2. Do not worship idols
3. Do not use G-d's name in vain
4. Remember Shabbos to keep it holy
5. Honor your father and mother
6. You shall not kill
7. You shall not commit adultery
8. You shall not steal
9. You shall not be a false witness
10. You shall not be jealous of your friend's possessions

It is a custom that we all stand while listening to the 10 Commandments being read.