Exodus 12:15-18 - The Festival Of Unleavened Bread
15 You will eat unleavened bread for seven days. The first day you shall remove leaven from your houses. Whoever eats anything leavened from the first day until the seventh day will be cut off from Israel. 16 You shall have a holy assembly on the first day. There should be another holy assembly on the seventh day. No work at all will be done on them, except what must be eaten by every person that alone may be prepared by you.
17 You shall also observe the Feast of Unleavened Bread. That was the day I brought your hosts out of the land of Egypt. Observe this day throughout your generations as a long lasting ordinance. 18 In the first month, on the fourteenth day of the month at evening, you shall eat unleavened bread, until the twenty-first day of the month at evening.