Exodus 13:11-16 - The Feast Of Unleavened Bread
11 And it will be, when Jehovah shall bring you into the land of the Canaanites, as He swore to you and to your fathers, and shall give it to you, 12 you shall set apart to Jehovah every one that opens the womb, and every first-born that comes of any animal which you have; the males shall be Jehovah's. 13 And every first-born of an ass you shall redeem with a lamb. And if you will not redeem it, then you shall break its neck. And all the first-born of man among your sons you shall redeem.
14 And it shall be when your sons asks you in time to come, saying, What is this? you shall say to him, Jehovah brought us out of Egypt by the strength of His hand, from the house of bondage. 15 And it happened when Pharaoh hardened himself against sending us, Jehovah killed all the first-born of the land of Egypt, both the first-born of man, and the first-born of animals. Therefore I sacrifice to Jehovah all that opens the womb, that are males. But all the first-born of my sons I redeem. 16 And it shall be for a token upon your hand, and for frontlets between your eyes. For Jehovah brought us out from Egypt by strength of His hand.