Exodus 31:13-17

13“But as for you, say to the Israelites, ‘You shall most certainly observe My Sabbaths, for it is a sign between Me and you throughout your generations, so that you may know [without any doubt] and acknowledge that I am the Lord who sanctifies you and sets you apart [for Myself].

14Therefore, you shall keep the Sabbath, for it is holy to you. Everyone who profanes it must be put to death; for whoever does work on the Sabbath, that person (soul) shall be cut off from among his people [excluding him from the atonement made for them].

15For six days work may be done, but the seventh is the Sabbath of complete rest, sacred to the Lord; whoever does work on the Sabbath day must be put to death.

16So the Israelites shall observe the Sabbath, to celebrate the Sabbath throughout their generations as a perpetual covenant.’

17It is a sign between Me and the Israelites forever; for in six days the Lord made the heavens and the earth, and on the seventh day He ceased and was refreshed.”