Exodus 4:24

22You shall tell Pharaoh, ‘The LORD says, Israel is my son, my firstborn,

23and 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 firstborn son.’”

24On the way at a lodging place, the LORD met Moses and wanted to kill him.

25Then Zipporah took a flint, and cut off the foreskin of her son, and cast it at his feet; and she said, “Surely you are a bridegroom of blood to me.”

26So he let him alone. Then she said, “You are a bridegroom of blood,” because of the circumcision.