Exodus 4:22-23
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.
Bible text: American Standard Version (1901) · Public domain