For he is not a Jew, which is one outwardly; neither [is that] circumcision, which is outward in the flesh:
Note 1 at Ro 2:28: As with so many commandments of the Old Testament, circumcision was an outward sign of a greater inward reality. Paul used this term "sign" in referring to the circumcision of Abraham in Ro 4:11. The Jews of the first century had ignored the circumcision of the heart and had focused all their attention on the flesh (1Sa 16:7). Paul was clarifying that it is the condition of the heart--not the flesh--that makes someone a child of God.