Leviticus 23:6-8

The Feast of Unleavened Bread to the LORD is on the fifteenth day of the same month; for seven days you shall eat unleavened bread. [1 Cor 5:7, 8] On the first day you shall have a holy convocation (calling together); you shall not do any laborious work [on that day]. But you shall present an offering by fire to the LORD for seven days; on the seventh day there shall be a holy convocation; you shall not do any laborious work [on that day].’ ”