Exodus 31
15 Ref Six days may work be done, but the seventh day is a Sabbath of complete rest, holy to the Lord; whoever does any work on the Sabbath day is to be put to death.
16 Ref And the children of Israel are to keep the Sabbath holy, from generation to generation, by an eternal agreement.
17 Ref It is a sign between me and the children of Israel for ever; because in six days the Lord made heaven and earth, and on the seventh day he took his rest and had pleasure in it.