Exodus 31:13-16

13“Say to the Israelites, ‘You must observe my Sabbaths. This will be a sign between me and you for the generations to come, so you may know that I am the Lord, who makes you holy. 14“ ‘Observe the Sabbath, because it is holy to you. Anyone who desecrates it is to be put to death; those who do any work on that day must be cut off from their people. 15For six days work is to be done, but the seventh day is a day of sabbath rest, holy to the Lord. Whoever does any work on the Sabbath day is to be put to death. 16The Israelites are to observe the Sabbath, celebrating it for the generations to come as a lasting covenant.