The Sabbath is not mentioned in Genesis 1-2.
2 "I am the Lord your God, who brought you out of the land of Egypt, out of the house of bondage.
3 "You shall have no other gods before Me. (Exodus 20:2-3)
The Book of Job states:
21 Blessed be the name of the LORD (Job 1:21).
28 This also would be an iniquity deserving of judgement,
For I would have denied God who is above (Job 31:28).
1 The Job answered the LORD and said: 'I know that You can do everything,
and that no purpose of Yours can be withheld from You' (Job 42:1-2).
28 And to man He said, 'Behold, the fear of the Lord, that is wisdom,
and to depart from evil is understanding' (Job 28:28).
What is interesting about Job 28:28 is that Job said that this is what God said to man
and there is no record of this being said in Genesis (which is the primary biblical book
with information prior to the story of Job), thus this verse proves that God spoke to
humankind prior to Moses in at least one way that was not recorded in Genesis.
Thus this refutes the argument that none prior to Mount Sinai could have known what
the commandments were! If there were no commandments in effect, how could denying
God be an iniquity deserving of judgement?