Exodus 4:20-26

20And Moses took his wife and his sons, and set them riding upon an ass, and he returned to the land of Egypt. And Moses took the staff of 1God in his hand.

21And Jehovah said to Moses, When thou goest to return to Egypt, see that thou do all the wonders before Pharaoh that I have put in thy hand. And I will harden his heart, that he shall not let the people go.

22And thou shalt say to Pharaoh, Thus saith Jehovah: Israel is my son, my firstborn.

23And I say to thee, Let my son go, that he may serve me. And if thou refuse to let him go, behold, I will kill thy son, thy firstborn.

24And it came to pass on the way, in the inn, that Jehovah came upon him, and sought to slay him.

25Then Zipporah took a stone and cut off the foreskin of her son, and cast it at his feet, and said, A bloody husband indeed art thou to me!

26And he let him go. Then she said, A bloody husband — because of the circumcision.