Exodus 12:15-20
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 34:18
You are to observe the Feast of Unleavened Bread. For seven days at the appointed time in the month of Abib, you are to eat unleavened bread as I commanded you. For in the month of Abib you came out of Egypt.

Leviticus 23:8
For seven days you are to present an offering made by fire to the LORD. On the seventh day there shall be a sacred assembly; you must not do any ordinary work.'"