Exodus 31:14-15

You must keep the Sabbath day, for it is a holy day for you. Anyone who desecrates it must be put to death; anyone who works on that day will be cut off from the community. You have six days each week for your ordinary work, but the seventh day must be a Sabbath day of complete rest, a holy day dedicated to the LORD. Anyone who works on the Sabbath must be put to death.