Exodus 4:22-23

Exodus 4:22-23

[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.