After the Lord explained to Moses why Israel was to keep the Sabbath, the Bible says,

And when He had made an end of speaking with him on Mount Sinai, He gave Moses two tablets of the Testimony, tablets of stone, written with the finger of God (Exodus 31.18).

Think of the magnificent statements made in this verse:

God had been speaking with Moses.
God gave Moses the two tablets of the Testimony, otherwise, known as The Ten Commandments.
God had written on the tablets of stone with His finger.

The time that Moses spent with God just boggles the mind.