Exodus 13:2, 12-15

Sanctify unto me all the first-born, whatsoever openeth the womb among the children of Israel, both of man and of beast: it is mine.

that thou shalt set apart unto Jehovah all that openeth the womb, and every firstling which thou hast that cometh of a beast; the males shall be Jehovah’s. And every firstling of an ass thou shalt redeem with a lamb; and if thou wilt not redeem it, then thou shalt break its neck: and all the first-born of man among thy sons shalt thou redeem. And it shall be, when thy son asketh thee in time to come, saying, What is this? that thou shalt say unto him, By strength of hand Jehovah brought us out from Egypt, from the house of bondage: and it came to pass, when Pharaoh would hardly let us go, that Jehovah slew all the first-born in the land of Egypt, both the first-born of man, and the first-born of beast: therefore I sacrifice to Jehovah all that openeth the womb, being males; but all the first-born of my sons I redeem.