Exodus 4:21-23

21st Century King James Version

²¹ And the Lord said unto Moses, “When thou goest to return into Egypt, see that thou do all those wonders before Pharaoh which I have put in thine hand; but I will harden his heart, that he shall not let the people go.

²² And thou shalt say unto Pharaoh, ‘Thus saith the Lord: Israel is My son, even My firstborn.

²³ And I say unto thee, “Let My son go, that he may serve Me.” And if thou refuse to let him go, behold, I will slay thy son, even thy firstborn.’”