John Chrysostom

"Do we then," he says, "make void the Law through faith? God forbid: yea, we establish the Law." Do you see his varied and unspeakable judgment? For the bare use of the word "establish" shows that it was not then standing, but was worn out. And note also Paul's exceeding power, and how superabundantly he maintains what he wishes. For here he shows that the faith, so far from doing any disparagement to the "Law," even assists it, as it on the other hand paved the way for the faith. …

Homily on Romans 7 ↗

Theophylact of Ohrid

The statement that the law is overthrown by faith threw the Jews into confusion. Therefore he heals them with his great wisdom, saying that faith establishes the law. For what the law also desired, that is, to justify man, but could not do, faith accomplishes. Whoever has believed has already been justified. So faith did not destroy, but established the law. By the expression ίστώμεν he suggests that the law was lying down, and that which is lying down must be raised up and set upright.

Commentary on Romans ↗

Thomas Aquinas

Then when he says do we then destroy, he excludes an objection. For someone might claim that he is overthrowing the aforementioned law; therefore, he asks: do we then destroy the law through faith, inasmuch as we say that men are justified without the works of the law? He answers: God forbid! in keeping with Matthew, not an iota, not a dot, will pass from the law (Matt 5:18). …

Commentary on Romans ↗