Thomas Aquinas — on Rom 3:30 (Commentary on Romans)

“Third, at for it is one God, he manifests what he had said with a sign, as if to say: it is clear that he is the God not only of the Jews but also of the gentiles, for it is one God who justifies circumcision, i.e., the Jews, from faith, as is said in Galatians, in Christ Jesus neither circumcision nor uncircumcision is of any avail (Gal 5:6). According to the Gloss, from faith and through faith are exactly the same. However, a slight difference can be noted. For the preposition 'from' sometimes designates a remote cause, while the preposition 'through' designates a nearer cause. Therefore, the Jews are said to be justified from faith because faith was the first cause from which circumcision and the other sacraments of the law proceeded; thus, faith justified the Jews as a primary cause through intermediate causes. But the gentiles are justified by faith itself immediately.”