Deuteronomy 16:3-4

NSB(i) 3 »Do not eat leavened bread with it. Eat unleavened bread for seven days. It is the bread of affliction. You should remember all the days of your life the day when you came out of the land of Egypt in haste. 4 »No leaven should be seen with you in all your territory for seven days. None of the flesh you sacrifice on the evening of the first day shall remain overnight until morning.