Deuteronomy 16:3; Deuteronomy 16:4

3 "You shall not eat leavened bread with it; seven days you shall eat with it unleavened bread, the bread of affliction (for you came out of the land of Egypt in haste ), so that you may remember all the days of your life the day when you came out of the land of Egypt.

4 "For seven days no leaven shall be seen with you in all your territory, and none of the flesh which you sacrifice on the evening of the first day shall remain overnight until morning.