Exodus 13:11-16

11"When the Lord brings you into the land of the Canaanites, as he swore to you and your fathers, and shall give it to you,

12you shall set apart to the Lord all that first opens the womb. All the firstborn of your animals that are males shall be the Lord's.

13Every firstborn of a donkey you shall redeem with a lamb, or if you will not redeem it you shall break its neck. Every firstborn of man among your sons you shall redeem.

14And when in time to come your son asks you, 'What does this mean?' you shall say to him, 'By a strong hand the Lord brought us out of Egypt, from the house of slavery.

15For when Pharaoh stubbornly refused to let us go, the Lord killed all the firstborn in the land of Egypt, both the firstborn of man and the firstborn of animals. Therefore I sacrifice to the Lord all the males that first open the womb, but all the firstborn of my sons I redeem.'

16It shall be as a mark on your hand or frontlets between your eyes, for by a strong hand the Lord brought us out of Egypt."