Exodus 13:1-2, 11-16
The LORD said to Moses: Consecrate to me all the firstborn; whatever is the first to open the womb among the Israelites, of human beings and animals, is mine.
The Consecration of the Firstborn
“When the LORD has brought you into the land of the Canaanites, as he swore to you and your ancestors, and has given it to you, you shall set apart to the LORD all that first opens the womb. All the firstborn of your livestock that are males shall be the LORD's. But every firstborn donkey you shall redeem with a sheep; if you do not redeem it, you must break its neck. Every firstborn male among your children you shall redeem. When in the future your child asks you, ‘What does this mean?’ you shall answer, ‘By strength of hand the LORD brought us out of Egypt, from the house of slavery. When Pharaoh stubbornly refused to let us go, the LORD killed all the firstborn in the land of Egypt, from human firstborn to the firstborn of animals. Therefore I sacrifice to the LORD every male that first opens the womb, but every firstborn of my sons I redeem.’ It shall serve as a sign on your hand and as an emblem on your forehead that by strength of hand the LORD brought us out of Egypt.”