Exodus 13:5-7

5And it shall be when Jehovah hath brought thee into the land of the Canaanite and the Hittite and the Amorite and the Hivite and the Jebusite, which he swore to thy fathers to give thee, a land flowing with milk and honey, that thou shalt keep this service in this month.

6Seven days shalt thou eat unleavened bread; and in the seventh day is a feast to Jehovah.

7Unleavened bread shall be eaten the seven days; and leavened bread shall not be seen with thee, neither shall there be leaven seen with thee in all thy borders.