Exodus 4:20-26

20So Moses took his wife [Zipporah] and his sons [Gershom and Eliezer] and seated them on donkeys, and returned to the land of Egypt. Moses also took the staff of God in his hand.

21The Lord said to Moses, “When you return to Egypt, see that you perform before Pharaoh all the wonders (miracles) which I have put in your hand, but I will harden his heart and make him stubborn so that he will not let the people go.

22Then you shall say to Pharaoh, ‘Thus says the Lord, “Israel is My son, My firstborn.

23So I say to you, ‘Let My son go so that he may serve Me’; and if you refuse to let him go, behold, I will kill your son, your firstborn.” ’ ”

24Now it happened at the lodging place, that the Lord met Moses and sought to kill him [making him deathly ill because he had not circumcised one of his sons].

25Then Zipporah took a flint knife and cut off the foreskin of her son and threw it at Moses’ feet, and said, “Indeed you are a husband of blood to me!”

26So He let Moses alone [to recover]. At that time Zipporah said, “You are a husband of blood”—because of the circumcision.