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. 5 In the first month, on the fourteenth day of the month at twilight, is the LORD’s Passover. 6 And 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. 7 On the first day you shall have a holy convocation; you shall not do any ordinary work. 8 But 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.”
(ESV)