Exodus 12:15-18 - The Festival Of Unleavened Bread
15 You shall eat unleavened bread seven days; even the first day you shall put away leaven out of your houses. For whoever eats leavened bread from the first day until the seventh day, that soul shall be cut off from Israel. 16 And on the first day shall be a holy gathering, and in the seventh day there shall be a holy gathering for you. No manner of work shall be done in them, except that which every man must eat, that only may be done by you.
17 And you shall keep the Feast of Unleavened Bread. For in this same day I have brought your armies out of the land of Egypt. Therefore you shall keep this day in your generations by a law forever. 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.