Exodus 4 - Moses argues with God about sending him to speak to Pharaoh. God reminds Moses that He made man able to speak. God said Aaron would be the mouthpiece for Moses. When asked for His name, God said, "I AM that I AM."
Exodus 5 - Moses and Aaron appear before Pharaoh and tell him to let Israel go. Pharaoh not only rejects their demand but he also adds to Israel's affliction causing even greater pain for the people. The Israelites then complain to Moses for his interference and Moses complains to God. Moses was made to realize it wasn't his strength or authority that would change Pharaoh's heart, it would have to be God's.
Exodus 6 - God tells Moses, that He, God, would show what He can do. Moses would learn to rely upon God. Moses is told to go back to Pharaoh even though Moses said the people of Israel wouldn't even listen to him. The ancestry of Aaron and Moses is revealed in this chapter.