Deuteronomy 16:2-4

New Century Version

² As the sacrifice for the Passover to the Lord your God, offer an animal from your flock or herd at the place the Lord will choose to be worshiped. ³ Do not eat it with bread made with yeast. But for seven days eat bread made without yeast, the bread of suffering, because you left Egypt in a hurry. So all your life you will remember the time you left Egypt. ⁴ There must be no yeast anywhere in your land for seven days. Offer the sacrifice on the evening of the first day, and eat all the meat before morning; do not leave it overnight.