The LORD then gave these instructions to Moses:
“Tell the people of Israel: ‘Be careful to keep my Sabbath day, for the Sabbath is a sign of the covenant between me and you from generation to generation. It is given so you may know that I am the LORD, who makes you holy.
You must keep the Sabbath day, for it is a holy day for you. Anyone who desecrates it must be put to death; anyone who works on that day will be cut off from the community.
You have six days each week for your ordinary work, but the seventh day must be a Sabbath day of complete rest, a holy day dedicated to the LORD . Anyone who works on the Sabbath must be put to death.
The people of Israel must keep the Sabbath day by observing it from generation to generation. This is a covenant obligation for all time.
It is a permanent sign of my covenant with the people of Israel. For in six days the LORD made heaven and earth, but on the seventh day he stopped working and was refreshed.’”
When the LORD finished speaking with Moses on Mount Sinai, he gave him the two stone tablets inscribed with the terms of the covenant, written by the finger of God.
References for Exodus 31:18