Exodus 12:7 (KJV)

This month shall be unto you the beginning of months: it shall be the first month of the year to you.

Speak ye unto all the congregation of Israel, saying, In the tenth day of this month they shall take to them every man a lamb, according to the house of their fathers, a lamb for an house:

And if the household be too little for the lamb, let him and his neighbour next unto his house take it according to the number of the souls; every man according to his eating shall make your count for the lamb.

Your lamb shall be without blemish, a male of the first year: ye shall take it out from the sheep, or from the goats:

And ye shall keep it up until the fourteenth day of the same month: and the whole assembly of the congregation of Israel shall kill it in the evening.

And they shall eat the flesh in that night, roast with fire, and unleavened bread; and with bitter herbs they shall eat it.

Eat not of it raw, nor sodden at all with water, but roast with fire; his head with his legs, and with the purtenance thereof.

And ye shall let nothing of it remain until the morning; and that which remaineth of it until the morning ye shall burn with fire.

And thus shall ye eat it; with your loins girded, your shoes on your feet, and your staff in your hand; and ye shall eat it in haste: it is the LORD's passover.

For I will pass through the land of Egypt this night, and will smite all the firstborn in the land of Egypt, both man and beast; and against all the gods of Egypt I will execute judgment: I am the LORD.