Rom 4:12

“Here again he lays low the lofty spirit of the Jews by reminding them of the time of the justification. And he well says, "the steps," that you as well as Abraham may believe in the resurrection of bodies that are dead. For he also displayed his faith upon this point. And so if you reject the uncircumcision, be informed for certain that the circumcision is of no more use unto you. For if you follow not in the steps of his faith, though you were ten thousand times in a state of circumcision, you will not be Abraham's offspring. For even he received the circumcision for this end, that the man in a state of uncircumcision might not cast thee off. Do not then demand this of him too. For it was you whom the thing was to be an assistance to, not he. But he calls it a sign of the righteousness. And this also was for thy sake, since now it is not even this: for thou then wert in need of bodily signs, but now there is no need of them.”

“Therefore all the Gentiles who believe are children of Abraham when faith alone is credited to them as righteousness and they too receive the circumcision—of the heart. Or perhaps this verse should be understood like this: Abraham was righteous in uncircumcision so that he could become the father of uncircumcised believers, and he remained righteous once he was circumcised in order to become the father of the righteous who are circumcised.”

“If a Gentile who has not been circumcised follows Abraham's faith, which he manifested before being circumcised, he will not be rejected. For the God of all, since he had foreseen as God that he would gather one people from both Jews and Gentiles and prepare for them salvation by faith, had appointed Abraham as their father as well. Paul had demonstrated that Abraham had acquired righteousness by faith before being circumcised and that even after being circumcised he lived not according to the law of Moses but by clinging to his faith. Hence Paul called him the father of the Gentiles who believe.”

“Through circumcision Abraham proves to be the father of "the circumcision," that is, of the circumcised. Yet he is the father not only of those who have circumcision, but also of those who walk in the footsteps of the faith that he had while in uncircumcision. So, the present passage must be read thus: he became the father of the circumcised not for those who resemble him in circumcision alone, but for those who walk in the footsteps of his faith, that is, who like him believe in the resurrection of dead bodies. For in old age and in deadness he believed that God could make his seed fruitful and give him a son. The complete thought is this: Abraham, being uncircumcised, believed and was justified, so that in this way he might become the father of believing uncircumcised ones. On the other hand, he received circumcision, a seal and sign of the faith which was in uncircumcision, so as to become the father of the circumcised who walk, of course, in the footsteps of his faith which he had while not yet circumcised. As long as this faith is absent, circumcision boasts in vain, imitating one who shows a purse to which only a seal has been affixed, but in which there is nothing. So then, the Jew is a purse sealed by circumcision, but not having the faith whose seal is circumcision.”

“Then he shows the manner in which he is the father even of the uncircumcised, namely, by imitation. And this is what he says: that he might be the father . . . not to those only who are of the circumcision, but to those also who follow the steps of the faith that is in the uncircumcision of our father Abraham, i.e., which Abraham had, while he was still uncircumcised: if you were Abraham's children, you would do what Abraham did (John 8:39).”

“Paul says this because Abraham by believing became the forefather of the circumcision, but of the heart, not only of those who descended from him but also of those who, from among the nations, believed in the way he did. He is the father of the Jews according to the flesh, but according to faith he is the father of all believers.”