Exodus 12:15-18

15Seven days shall ye eat unleavened bread; even the first day ye shall put away leaven out of your houses: for whosoever eateth leavened bread from the first day until the seventh day, that soul shall be cut off from Israel.

16And in the first day there shall be to you an holy convocation, and in the seventh day an holy convocation; no manner of work shall be done in them, save that which every man must eat, that only may be done of you.

17And ye shall observe the feast of unleavened bread; for in this selfsame day have I brought your hosts out of the land of Egypt: therefore shall ye observe this day throughout your generations by an ordinance for ever.

18In the first month, on the fourteenth day of the month at even, ye shall eat unleavened bread, until the one and twentieth day of the month at even.