Exodus 4:23 ASV

²¹  And Jehovah said unto Moses, When thou goest back into Egypt, see that thou do before Pharaoh all the wonders which I have put in thy hand: but I will harden his heart and he will not let the people go.

²²  And thou shalt say unto Pharaoh, Thus saith Jehovah, Israel is my son, my first-born:

²³  and I have said unto thee, Let my son go, that he may serve me; and thou hast refused to let him go: behold, I will slay thy son, thy first-born.

²⁴  And it came to pass on the way at the lodging-place, that Jehovah met him, and sought to kill him.

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