Exodus 12:3, 11-13

Tell the whole congregation of Israel that on the tenth of this month they are to take a lamb for each family, a lamb for each household. This is how you shall eat it: your loins girded, your sandals on your feet, and your staff in your hand; and you shall eat it hurriedly. It is the passover of the Lord. For I will pass through the land of Egypt that night, and I will strike down every firstborn in the land of Egypt, both human beings and animals; on all the gods of Egypt I will execute judgements: I am the Lord. The blood shall be a sign for you on the houses where you live: when I see the blood, I will pass over you, and no plague shall destroy you when I strike the land of Egypt.