Exodus 12:15-17
For seven days you must eat unleavened bread. On the first day you are to remove the yeast from your houses. Whoever eats anything leavened from the first day through the seventh must be cut off from Israel. . . .

Exodus 13:6
For seven days you are to eat unleavened bread, and on the seventh day there shall be a feast to the LORD.

Leviticus 23:6
On the fifteenth day of the same month begins the Feast of Unleavened Bread to the LORD. For seven days you must eat unleavened bread.