God had laws and commandments before he made a covenant with Israel. One of these was the Sabbath, which was made at creation. It's part of the fabric of God's creation.
Chapter and verse?
Show us where Abraham was commanded in regard to Sabbath keeping.
Wrong, the Sabbath was for the Jews and stated as an example of God who took a day of rest, but our rest is in Christ Jesus. What Mark wrote pointed to Jesus pointing to himself as being the Sabbath rest
As Matthew wrote in Matt 11:28 Come to Me, all you who labor and are heavy laden, and I will give you rest.
The rest He speaks of is in HIM, not in a stupid day.
Not until Exodus do we read GOD telling them to rest as He did, but before that He never did.