Exodus 13:1-2, 11-16
The LORD said to Moses, "Consecrate to me all the first-born; whatever is the first to open the womb among the people of Israel, both of man and of beast, is mine.
"And 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, 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. 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. 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. For when Pharaoh stubbornly refused to let us go, the LORD slew all the first-born in the land of Egypt, both the first-born of man and the first-born of cattle. Therefore I sacrifice to the LORD all the males that first open the womb; but all the first-born of my sons I redeem.' It 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."