In Genesis 26 we read this:
I will make your descendants as many as the stars of heaven, and I will give them all these lands; and all the nations in the world shall bless themselves by your descendants in return for Abraham’s obedience; for he kept my charge, my commandments, my statutes and my laws. [26:4–5]
Abraham was righteous, God says, because of what he did. This contradicts the Reformed/Presbyterian notion that there is no one who does good.
Furthermore, it seems that there must have been an oral tradition of God’s commandments, statutes, and laws that was kept by Abraham, because there is nothing whatsoever to suggest that God provided a written code for him or his ancestors (the book of Genesis was written centuries later). Consequently it seems safe to say that a written law is not a sine qua non of how God deals with His people, and that appeals to tradition as divine laws cannot be ipso facto rejected.