Exod 4:24-26

24On the way, at a place where they spent the night, the Lord met him and tried to kill him.25But Zipporah took a flint and cut off her son's foreskin, and touched Moses' feet with it, and said, “Truly you are a bridegroom of blood to me!”26So he let him alone. It was then she said, “A bridegroom of blood by circumcision.”