The Lord said to Moses:
References for Exodus 31:12
"Tell the Israelites: You must observe My Sabbaths, for it is a sign between Me and you throughout your generations, so that you will know that I am the Lord who sets you apart.
Observe the Sabbath, for it is holy to you. Whoever profanes it must be put to death. If anyone does work on it, that person must be cut off from his people.
For six days work may be done, but on the seventh day there must be a Sabbath of complete rest, dedicated to the Lord. Anyone who does work on the Sabbath day must be put to death.
The Israelites must observe the Sabbath, celebrating it throughout their generations as a perpetual covenant.
It is a sign forever between Me and the Israelites, for in six days the Lord made the heavens and the earth, but on the seventh day He rested and was refreshed."
When He finished speaking with Moses on Mount Sinai, He gave him the two tablets of the testimony, stone tablets inscribed by the finger of God.
References for Exodus 31:18