God "gifted" Abram with credited righteousness (Gen 15) BEFORE he was given the sign of the covenant - circumcision. So Abram had faith in God by believing what God said BEFORE he ever given the sign in the natural. So Abram like the rest of us after the resurrection was released from the penalty of sin by faith in God. This is called grace. Notice however the same is said of Noah in Gen 6. He was considered righteous, even though Paul says that Abram was the father of credited righteousness by faith. In 2 Sam 11, David commits adultery with Bathsheba and has her husband killed in battle to have Bathsheba. However, in 2 Sam 12, Nathan, the prophet, tells David that he will not get the just punishment of death, but his son that came from adultery will die. This is grace operating - a gift of righteousness that is not deserved! Paul is showing the power of faith which grants access to grace. These are phenomenal and fundamental principles that must be ever present in our systematic theology. Abram wasn't given a covenant with God BECAUSE he was righteous, he was made righteous by FAITH. Since Abram was gifted before he was circumcised as a sign of the covenant, this is prima facie evidence that physical identity is not a prerequisite to blessings from God as many of the Jewish converts to Christianity wanted to claim. Abraham therefore becomes the father of both the spiritually circumcised AND the physically circumcised. This shows that although physical circumcision is essential under the Law, spiritual circumcision that comes by faith is essential under the elevated Law of the Gospel! Praise Him.