Exodus 13:11-16 - The Feast Of Unleavened Bread
11 "It shall be, when Yahweh shall bring you into the land of the Canaanite, as he swore to you and to your fathers, and shall give it you, 12 that you shall set apart to Yahweh all that opens the womb, and every firstborn which you have that comes from an animal. The males shall be Yahweh's. 13 Every firstborn of a donkey you shall redeem with a lamb; and if you will not redeem it, then you shall break its neck; and you shall redeem all the firstborn of man among your sons.
14 It shall be, when your son asks you in time to come, saying, 'What is this?' that you shall tell him, 'By strength of hand Yahweh brought us out from Egypt, from the house of bondage; 15 and it happened, when Pharaoh would hardly let us go, that Yahweh killed all the firstborn in the land of Egypt, both the firstborn of man, and the firstborn of animal. Therefore I sacrifice to Yahweh all that opens the womb, being males; but all the firstborn of my sons I redeem.' 16 It shall be for a sign on your hand, and for symbols between your eyes: for by strength of hand Yahweh brought us forth out of Egypt."