How - In what circumstances, or time.
When he was in circumcision ... - 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 pretend that it was in 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 set up; and the argument of the apostle was confirmed by the case of Abraham, the great father and model of the Jewish people, that circumcision and the deeds of the Law did not conduce to justification; and that as Abraham was justified without those works, so might others be, and the pagan, therefore, 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; Compare Genesis 17:10.