18 Moses went and returned to Jethro his father-in-law, and said to him, “Please let me go and return to my brothers who are in Egypt, and see whether they are still alive.”
Jethro said to Moses, “Go in peace.” 19 Yahweh said to Moses in Midian, “Go, return into Egypt; for all the men who sought your life are dead.” 20 Moses took his wife and his sons, and set them on a donkey, and he returned to the land of Egypt. Moses took God’s rod in his hand. 21 Yahweh said to Moses, “When you go back into Egypt, see that you do before Pharaoh all the wonders which I have put in your hand, but I will harden his heart and he will not let the people go. 22 You shall tell Pharaoh, ‘Thus says Yahweh, Israel is my son, my firstborn, 23 and I have said to you, “Let my son go, that he may serve me;” and you have refused to let him go. Behold, I will kill your son, your firstborn.’”
Matthew Henry's Commentary on Exodus 4:18-23
Commentary on Exodus 4:18-23
(Read Exodus 4:18-23)
After God had appeared in the bush, he often spake to Moses. Pharaoh had hardened his own heart against the groans and cries of the oppressed Israelites; and now God, in the way of righteous judgment, hardens his heart against the teaching of the miracles, and the terror of the plagues. But whether Pharaoh will hear, or whether he will forbear, Moses must tell him, Thus saith the Lord. He must demand a discharge for Israel, Let my son go; not only my servant, whom thou hast no right to detain, but my son. It is my son that serves me, and therefore must be spared, must be pleaded for. In case of refusal I will slay thy son, even thy first-born. As men deal with God's people, let them expect so to be dealt with.