Albert Barnes Commentary Romans 4:10

"How then was it reckoned? when he was in circumcision, or in uncircumcision? Not in circumcision, but in uncircumcision:" — Romans 4:10 (ASV)

How. In what circumstances, or time.

When he was in circumcision, and so forth. Before or after he was circumcised? This was the very point of the inquiry. For if he was justified by faith after he was circumcised, the Jew might claim that it was by virtue of his circumcision; that even his faith was acceptable because he was circumcised. But if it was before he was circumcised, this plea could not be advanced; and the apostle's argument was confirmed by the case of Abraham, the great father and model of the Jewish people. This case demonstrated that circumcision and the deeds of the law did not contribute to justification, and that, just as Abraham was justified without those works, so others might also be. Therefore, the Gentiles might be admitted to similar privileges.

Not in circumcision. Not being circumcised, or after he was circumcised, but before. This was the record in the case, Genesis 15:6. .