Exodus 13:12-14 Revised Standard Version (RSV)
12 you shall set apart to the Lord all that first opens the womb. All the firstlings of your cattle that are males shall be the Lord’s. 13 Every firstling of an ass you shall redeem with a lamb, or if you will not redeem it you shall break its neck. Every first-born of man among your sons you shall redeem. 14 And when in time to come your son asks you, ‘What does this mean?’ you shall say to him, ‘By strength of hand the Lord brought us out of Egypt, from the house of bondage.