Romans 4:9,10 - Joseph Benson’s Commentary on the Old and New Testaments

Cometh this blessedness Mentioned by Abraham and David; on the circumcision Those that are circumcised only? or upon the uncircumcision also? The circumcision are the Jews, the members of God's visible church, and the uncircumcision are the Gentiles, who are out of the visible church. In this question, therefore, the justification of those who are out of the visible church, but who believe and obey God, is implied: for the apostle proves that such are justified, by appealing to Abraham's justification while in uncircumcision. Abraham was not circumcised till he was ninety-nine years old, Genesis 17:24. At that time Ishmael was thirteen years old, Romans 4:25. But before Ishmael was born, Abraham had his faith counted to him for righteousness, Genesis 15:6, compared with Genesis 16:16. It is evident, therefore, that Abraham was justified in uncircumcision more than thirteen years before he and his family were made the visible church and people of God by circumcision. Heathen, therefore, who believe and obey the true God, as Abraham did, will, like him, have their faith counted to them for righteousness, though no members of any visible church.