Moses went back to Jethro his father-in-law and said to him, “Please let me go back to my brothers in Egypt to see whether they are still alive.” And Jethro said to Moses, “Go in peace.” And the Lord said to Moses in Midian, “Go back to Egypt, for all the men who were seeking your life are dead.” So Moses took his wife and his sons and had them ride on a donkey, and went back to the land of Egypt. And Moses took the staff of God in his hand.

And the Lord said to Moses, “When you go back to Egypt, see that you do before Pharaoh all the miracles that I have put in your power. But I will harden his heart, so that he will not let the people go. Then you shall say to Pharaoh, ‘Thus says the Lord, Israel is my firstborn son, and I say to you, “Let my son go that he may serve me.” If you refuse to let him go, behold, I will kill your firstborn son.’” (ESV)