Exodus 13:5-7

5And it shall be, when the Lord brings you into the land of the Canaanites and the Hittites and the Amorites and the Hivites and the Jebusites, which He swore to your fathers to give you, a land flowing with milk and honey, that you shall keep this service in this month.

6Seven days you shall eat unleavened bread, and on the seventh day there shall be a feast to the Lord.

7Unleavened bread shall be eaten seven days. And no leavened bread shall be seen among you, nor shall leaven be seen among you in all your quarters.