Exodus 12:17-22 NIV
“Celebrate the Festival of Unleavened Bread, because it was on this very day that I brought your divisions out of Egypt. Celebrate this day as a lasting ordinance for the generations to come. In the first month 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 no yeast is to be found in your houses. And anyone, whether foreigner or native-born, who eats anything with yeast in it must be cut off from the community of Israel. Eat nothing made with yeast. Wherever you live, you must eat unleavened bread.” Then Moses summoned all the elders of Israel and said to them, “Go at once and select the animals for your families and slaughter the Passover lamb. Take a bunch of hyssop, dip it into the blood in the basin and put some of the blood on the top and on both sides of the doorframe. None of you shall go out of the door of your house until morning.