And the father of circumcision to them who are not of the circumcision only, but who also walk in the steps of that faith of our father Abraham, which he had being yet uncircumcised.
All Commentaries on Romans 4:12 Go To Romans 4
Ambrosiaster
AD 400
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. Commentary on Paul’s Epistles.