Exodus 12:13-15

13And the blood shall be to you for a token upon the houses where ye are : and when I see the blood, I will pass over you, and the plague shall not be upon you to destroy you, when I smite the land of Egypt.1

14And this day shall be to you for a memorial; and ye shall keep it a feast to the LORD throughout your generations; ye shall keep it a feast by an ordinance for ever.

15Seven days shall ye eat unleavened bread; even the first day ye shall put away leaven out of your houses: for whoever eateth leavened bread from the first day till the seventh day, that soul shall be cut off from Israel.