Therefore the people of Israel shall keep the Sabbath, observing the Sabbath throughout their generations, as a covenant forever. It is a sign forever between me and the people of Israel that in six days the Yehovah made heaven and earth, and on the seventh day he rested and was refreshed.’” And he gave to Moses, when he had finished speaking with him on Mount Sinai, the two tablets of the testimony, tablets of stone, written with the finger of God.
Exodus 31:16-18