Exodus 31:14-15

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.