Exodus 31:15-17

151For six days work may be done, but on the seventh day there is a 2Sabbath of complete rest, holy to the Lord; 3whoever does any work on the Sabbath day must be put to death. 16So the sons of Israel shall keep the Sabbath, to 4celebrate the Sabbath throughout their generations as a permanent covenant.’ 175It is a sign between Me and the sons of Israel forever; 6for in six days the Lord made heaven and earth, but on the seventh day He ceased from labor, and was refreshed.”