Leviticus 23:2-6

“Speak to the sons of Israel and say to them, ‘The Lord’s appointed times which you shall proclaim as holy convocations—My appointed times are these:

‘For six days work may be done, but on the seventh day there is a Sabbath of complete rest, a holy convocation. You shall not do any work; it is a Sabbath to the Lord in all your dwellings.

‘These are the appointed times of the Lord, holy convocations which you shall proclaim at the times appointed for them.

In the first month, on the fourteenth day of the month at twilight is the Lord’s Passover.

Then on the fifteenth day of the same month there is the Feast of Unleavened Bread to the Lord; for seven days you shall eat unleavened bread.