Exodus 31:15-17

15You may work for six days, but the seventh day is a day of rest—a holy day, a day when you don’t work. It is holy to the Lord. Whoever works on that day must be put to death.

16The Israelites must observe this day of rest as a holy day, celebrating it for generations to come as a permanent reminder of my promise.

17It will be a permanent sign between me and the Israelites, because the Lord made heaven and earth in six days, and on the seventh day he stopped working and was refreshed.’ ”