1st Day of Unleavened Bread

Then on the fifteenth day of the same month there is the Feast of Unleavened Bread to Yahweh; for seven days you shall eat unleavened bread. On the first day you shall have a holy convocation; you shall not do any laborious work. But for seven days you shall bring near an offering by fire to Yahweh. On the seventh day is a holy convocation; you shall not do any laborious work.

(Leviticus 23:6-8 LSB)