Exodus

⁹And it shall be for a sign unto thee upon thine hand, and for a memorial between thine eyes, that the law of the Lord may be in thy mouth: for with a strong hand hath the Lord brought thee out of Egypt. ¹⁰Thou shalt therefore keep this ordinance in its season from year to year. ¹¹And it shall be when the Lord shall bring thee into the land of the Canaanite, as he sware unto thee and to thy fathers, and shall give it thee, ¹²that thou shalt set apart unto the Lord all that openeth the womb, and every firstling which thou hast that cometh of a beast; the males shall be the Lord'S. ¹³And 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 firstborn of man among thy sons shalt thou redeem. ¹⁴And 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 the Lord brought us out from Egypt, from the house of bondage: ¹⁵and it came to pass, when Pharaoh would hardly let us go, that the Lord slew all the firstborn in the land of Egypt, both the firstborn of man, and the firstborn of beast: therefore I sacrifice to the Lord all that openeth the womb, being males; but all the firstborn of my sons I redeem.