Deuteronomy 16:3-4

3You are not to eat hametz with it. For seven days you are to eat matzot with it, the bread of affliction—for you came out from the land of Egypt in haste. Do this so that all the days of your life you will remember the day when you came out from the land of Egypt.

4No hametz should be seen with you in all your territory for seven days, and none of the meat you sacrifice on the evening of the first day may be left overnight until the morning.