Exodus 12:13-15

13The blood will be a sign for you on the houses where you are, and when I see the blood, I will pass over you. No destructive plague will touch you when I strike Egypt.

14“This is a day you are to commemorate; for the generations to come you shall celebrate it as a festival to the Lord—a lasting ordinance.

15For seven days you are to eat bread made without yeast. On the first day remove the yeast from your houses, for whoever eats anything with yeast in it from the first day through the seventh must be cut off from Israel.