Exodus 12:13-15

13The blood on the houses where you are staying will be a distinguishing mark for you; when I see the blood, I will pass over you. No plague will be among you to destroy you when I strike the land of Egypt.

14“This day is to be a memorial for you, and you must celebrate it as a festival to the Lord. You are to celebrate it throughout your generations as a permanent statute.

15You must eat unleavened bread for seven days. On the first day you must remove yeast from your houses. Whoever eats what is leavened from the first day through the seventh day must be cut off from Israel.