Leviticus 23:4-8

4"These are the appointed feasts of the Lord, the holy convocations, which you shall proclaim at the time appointed for them.

5In the first month, on the fourteenth day of the month at twilight, is the Lord's Passover.

6And on the fifteenth day of the same month is the Feast of Unleavened Bread to the Lord; for seven days you shall eat unleavened bread.

7On the first day you shall have a holy convocation; you shall not do any ordinary work.

8But you shall present a food offering to the Lord for seven days. On the seventh day is a holy convocation; you shall not do any ordinary work."