The fifth aliyah gives the Torah sources for the laws of divorce. A Jewish divorce requires a written get, placed into the woman's hand. Furthermore the divorced couple can't remarry if the woman remarried in between. The divorce of a Kohen is more complicated, he can't marry any divorced woman, even his own ex-wife. Therefore the "get" process of a Kohen is more involved to prevent "anger of the moment divorces". An interesting fact is that the Gomorra derives all of the Halachas (laws) of Jewish weddings from these few verses in the Torah about divorces.