In the sixth aliyah Moshe goes back to his father-in-law and asks permission to go back to Egypt, and his father-in-law says he should "go in peace." Moshe takes his wife and two sons and puts them on the donkey which Rashi says is the very same donkey as Avrohom Avinu used in the akaida, and that Moshiach will ride in the future, may it be speedily in our days, Amen.
G-d charges Moshe to warn Pharaoh that if he doesn't let the Jews (G-d's first born) go, He will slay Pharaoh's first born. (Rashi says that this confirms Esav's selling of the birthright to Yakov. Rashi also says that this is a lofty warning, warning Pharaoh of the ultimate punishment in advance, while a human would sneak up and attack unsuspected). On the way back to Egypt, Moshe's wife Tziporra performs a bris mila on her son Eliezer.