2). How Then Does Circumcision Affect The Issue As Illustrated In The Life Of Abraham? (4:9-12).
Paul now brings up with respect to Abraham the point that he had made in Romans 3:30, where he had claimed that God ‘will justify the circumcision by faith, and the uncircumcision through faith.' Here he asks, ‘Is this blessing (the blessing of not having sin reckoned to them, and of having righteousness reckoned to them) then pronounced on the circumcision, or on the uncircumcision also?' And his reply is that when Abraham believed God and was reckoned as righteous by faith he was not circumcised. Nor, he could have argued, was he circumcised until a good while after. Circumcision was nowhere related to his being accounted as righteous.
And we could add that that circumcision was not related to his being reckoned as righteous at any stage. It had rather to do with God's promises to Abraham, not only about Isaac and his descendants, but also about Ishmael and his descendants. In other words circumcision was much broader than Israel. Paul does not bring that out (to him the church was Israel), but he does stress that Abraham be seen as the father of us all, both circumcised and uncircumcised. He would no doubt in support of this have pointed back to other promises that Abraham had believed, after he had responded in faith to God, namely that he would be a blessing to the world (Genesis 12:3). All that being so, circumcision cannot be seen as necessary in order for a man to be reckoned as righteous by God. Only faith is necessary.