Exodus 31:12-18

And the LORD said to Moses, “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]. Therefore, 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]. For 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. So the Israelites shall observe the Sabbath, to celebrate the Sabbath throughout their generations as a perpetual covenant.’ It 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.” When He had finished speaking with him on Mount Sinai, He gave Moses the two tablets of the Testimony, tablets of stone, written with the finger of God.