Leviticus 23:1-3

Then ADONAI spoke to Moses saying: “Speak to Bnei-Yisrael, and tell them: These are the appointed moadim of ADONAI, which you are to proclaim to be holy convocations—My moadim. “Work may be done for six days, but the seventh day is a Shabbat of solemn rest, a holy convocation. You are to do no work—it is a Shabbat to ADONAI in all your dwellings.