Exodus 31:14-15

14Therefore you are to keep the Sabbath, for it is holy to you. 1Everyone who profanes it must be put to death; for whoever does any work on it, that person shall be cut off from among his people.

152For six days work may be done, but on the seventh day there is a 3Sabbath of complete rest, holy to the Lord; 4whoever does any work on the Sabbath day must be put to death.