Deuteronomy 16:3-4

31You shall not eat leavened bread with it; for seven days you shall eat unleavened bread with it, the bread of affliction (for you came out of the land of Egypt in a hurry), so that you will remember the day when you came out of the land of Egypt 2all the days of your life.

4For seven days no leaven shall be seen with you in your entire territory, and 3none of the meat which you sacrifice on the evening of the first day shall be left overnight until the morning.