Exodus 4:21-24

²¹ And the Lord told Moses, "When you arrive back in Egypt, go to Pharaoh and perform all the miracles I have empowered you to do. But I will harden his heart so he will refuse to let the people go. ²² Then you will tell him, 'This is what the Lord says: Israel is my firstborn son. ²³ I commanded you, "Let my son go, so he can worship me." But since you have refused, I will now kill your firstborn son!'"

²⁴ On the way to Egypt, at a place where Moses and his family had stopped for the night, the Lord confronted him and was about to kill him.