Leviticus 23:6-8

And on the fifteenth day of the same month is the Feast of Unleavened Bread to the LORD; seven days you must eat unleavened bread. On the first day you shall have a holy convocation; you shall do no customary work on it. But you shall offer an offering made by fire to the LORD for seven days. The seventh day shall be a holy convocation; you shall do no customary work on it.’ ”