Leviticus 23:3-6

³Six days shall ye do work: the seventh day, because it is the rest of the sabbath, shall be called holy. You shall do no work on that day: it is the sabbath of the Lord in all your habitations.

⁴These also are the holy days of the Lord, which you must celebrate in their seasons.

⁵The first month, the fourteenth day of the month at evening, is the phase of the Lord:

⁶And the fifteenth day of the same month is the solemnity of the unleavened bread of the Lord. Seven days shall you eat unleavened bread.