Exodus 12:17-22

You must celebrate the Feast of Unleavened Bread, because on this very day I brought your divisions of people out of Egypt. So all of your descendants must celebrate this day. This is a law that will last from now on. In the first month of the year you are to eat bread made without yeast, from the evening of the fourteenth day until the evening of the twenty-first day. For seven days there must not be any yeast in your houses. Anybody who eats yeast during this time, either an Israelite or non-Israelite, must be cut off from the community of Israel. During this feast you must not eat anything made with yeast. You must eat only bread made without yeast wherever you live.” Then Moses called all the elders of Israel together and told them, “Get the animals for your families and kill the lamb for the Passover. Take a branch of the hyssop plant, dip it into the bowl filled with blood, and then wipe the blood on the sides and tops of the doorframes. No one may leave that house until morning.