God instructs Moses to consecrate every firstborn male in commemoration of the day Israelites were freed from slavery (Exodus 13:1 – 13:16).
God said to Moses, “Consecrate to me every firstborn male. The first offspring of every womb belongs to me, whether human or animal.” Moses said to the people, “Commemorate this day, the day you came out of Egypt, out of the land of slavery, because the Lord brought you out of it with a mighty hand. Eat nothing containing yeast. Today, in the month of Aviv, you are leaving. When the Lord brings you into the land of the Canaanites, Hittites, Amorites, Hivites, and Jebusites, the land he swore to your ancestors to give to you, a land flowing with milk and honey, you are to observe this ceremony in this month. For seven days, eat bread made without yeast and on the seventh day, hold a festival