Exodus 31:15-17

For 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. The Israelites are to observe the Sabbath, celebrating it for the generations to come as a lasting covenant. It will be 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 rested and was refreshed.’ ”