Leviticus 23:4

2Speak unto the children of Israel, and say unto them, Concerning the feasts of the LORD, which ye shall proclaim to be holy convocations, even these are my feasts.

3Six days shall work be done: but the seventh day is the sabbath of rest, an holy convocation; ye shall do no work therein: it is the sabbath of the LORD in all your dwellings.

4These are the feasts of the LORD, even holy convocations, which ye shall proclaim in their seasons.

5In the fourteenth day of the first month at even is the LORD’s passover.

6And on the fifteenth day of the same month is the feast of unleavened bread unto the LORD: seven days ye must eat unleavened bread.