John Chrysostom
After this the Apostle sets forth the Jews' most grievous fault, saying, "You who boast in the law, through breaking the law you dishonor God."
He presented two faults, or more rightly, three. The Jews dishonor. They dishonor by what was appointed for their honor.
They dishonor Him Who gave them honor, and this is the summit of extreme ingratitude.
Paul brought forward two accusations, or rather three. They dishonor; they dishonor by what was intended for their honor; and they dishonor Him Who gave them honor.
This is the summit of extreme ingratitude. Then, lest he seem to accuse them on his own authority, he brings forward the prophet as their accuser.
Paul says: I am not reproaching you for this. Hear what Isaiah said: "Because of you the name of God is blasphemed among the nations" (Isa 52:5 LXX).