"This month shall be the beginning of months for you. It is to be the first month of the year to you. Speak to all the congregation of Israel, saying, 'On the tenth of this month they are each one to take a lamb for themselves, according to their fathers' households, a lamb for each household...
Your lamb shall be an unblemished male a year old. You may take it from the sheep or from the goats. You shall keep it until the fourteenth day of the same month, then the whole assembly of the congregation of Israel is to kill it at twilight. Moreover, they shall take some of the blood and put it on the two doorposts and on the lintel of the houses in which they eat it...
Now you shall eat it in this manner: with your loins girded, your sandals on your feet, and your staff in your hand, and you shall eat it in haste-- it is the LORD'S Passover.
For I will go through the land of Egypt on that night, and will strike down all the firstborn in the land of Egypt, both man and beast, and against all the gods of Egypt I will execute judgments-- I am the LORD!
The blood shall be a sign for you on the houses where you live. And when I see the blood I will pass over you, and no plague will befall you to destroy you, when I strike the land of Egypt!" Exodus 12, 1-13