John Gill

And the father of circumcision,.... So the Jews call Abraham (l), "the head of those that are circumcised"; and (m), "the head to them that are circumcised"; but the apostle here says, he is a father to them who are not of the circumcision only; not to the Jews only, in a spiritual sense, and not to all of them, since some were "of Israel", who were not Israel, not Israelites indeed, or true believers; but to such also who walk in the steps of that faith of our father Abraham, which he had, being yet uncircumcised; that is, who have the same faith he had; imitate and follow him in the exercise of faith; walk by faith, as he did when he was uncircumcised, as they are; and so the Jews say (n), "Abraham is the father of all, , "that go after him in his faith".'' (l) Tzeror Hammor, fol. 18. 3. (m) Juchasin, fol. 5. 2. Midrash Esther, fol. 85. 3. (n) R. Sol. Hammelech Michlol. Jophi in Mal. ii. 15.