Exodus 13:1-8 NRSV
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.
Moses said to the people, “Remember this day on which you came out of Egypt, out of the house of slavery, because the LORD brought you out from there by strength of hand; no leavened bread shall be eaten. Today, in the month of Abib, you are going out. When the LORD brings you into the land of the Canaanites, the Hittites, the Amorites, the Hivites, and the Jebusites, which he swore to your ancestors to give you, a land flowing with milk and honey, you shall keep this observance in this month. Seven days you shall eat unleavened bread, and on the seventh day there shall be a festival to the LORD. Unleavened bread shall be eaten for seven days; no leavened bread shall be seen in your possession, and no leaven shall be seen among you in all your territory. You shall tell your child on that day, ‘It is because of what the LORD did for me when I came out of Egypt.’
NRSV: New Revised Standard Version