Deuteronomy 16:3-4

3At this feast, eat bread that you make without any yeast. For seven days, you must eat bread that you make without yeast. You ate that kind of bread when you had much trouble in Egypt. You had to leave Egypt in a hurry that night. You must eat that bread each year. Then you will always remember the day when you left Egypt.

4During those seven days, no one may keep any yeast in their house. There must not be any yeast in the whole land. On the first day, you will kill your animal to eat in the evening. You must eat all the meat that same night, so that there is no meat left in the morning.