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 shall surely be put to death. 16So the sons of Israel shall observe the sabbath, to 4celebrate the sabbath throughout their generations as a perpetual 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.”