Moses asks God what he should do if the Israelites tell him to get lost.
God gives Moses three miracles to perform: His staff can now turn into a snake and back into a staff; his hand can turn leprous then become healthy again; and the water that Moses draws from the Nile can turn to blood. Cool bag of miracles.
Moses tells God that he's never been a great talker. God reminds Moses that he, God, created Moses's mouth, so it shouldn't be a big deal.
Just to be sure Pharaoh gets the message, God appoints Aaron, Moses's brother, to speak for Moses. God says to Moses, "He [Aaron] shall serve as a mouth for you, and you shall serve as God for him" (4:16). There's a chain of command here, folks.
Jethro, Moses's father-in-law, gives Moses permission to go back to Egypt, and Moses takes his wife and sons (notice how we only heard about the birth of one) on a donkey. Road trip!
God tells Moses to use the miracles, but says, "I will harden Pharaoh's heart, so that he will not let the people go" (4:21). God also threatens to kill Pharaoh's firstborn son if he doesn't let Moses do his thing.
Interlude time. Exodus 4:24-26 is a weird one. Here's the passage:
On the way, at a place where they spent the night, the Lord met him and tried to kill him. But Zipporah took a flint and cut off her son's foreskin, and touched Moses' feet with it, and said, "Truly you are a bridegroom of blood to me!" So he let him alone. It was then she said, "A bridegroom of blood by circumcision."
Hmmm. The trouble is, "him" in verse 24 could refer to Moses or Moses's son. Many scholars think that this passage is a point at which the writers wanted to replace child sacrifice with circumcision. Either way, it's a funky one, so heads up.
God commands Aaron to meet Moses at Mount Horeb. They hang out for a while, catch up, and then go assemble the Israelite elders. Aaron talks, Moses shows off his miracles, and the people decide that these guys should be in charge.