He solves one perplexity by another again. Yet as this is not clear, we must needs declare it more clearly. What is it then he means? God honored the Jews: they did despite to Him. This gives Him the victory, and shows the greatness of His love towards man, in that He honored them even such as they were. Since then, he means, we did despite to Him and wronged Him, God by this very thing became victorious, and His righteousness was shown to be clear. Why then (a man may say) am I to be punished, who have been the cause of His victory by the despite I did Him? Now how does he meet this? It is, as I was saying, by another absurdity again. For if it were you, he says, that were the cause of the victory, and after this are punished, the thing is an act of injustice. But if He is not unjust, and yet you are punished, then you are no more the cause of the victory. And note his apostolic reverence; (or caution: εὐλάβεια); for after saying, “Is God unrighteous Who takes vengeance?” he adds, “I speak as a man.” As if, he means, any body were to argue in the way men reason. For what things seem with us to be justice, these the just judgment of God far exceeds, and has certain other unspeakable grounds for it. Next, since it was indistinct, he says the same thing over again:
Ver. 7. “For if the truth of God has more abounded through my lie unto His glory: why yet am I also judged as a sinner?”
For if God, he means is shown to be a Lover of man, and righteous, and good, by your acts of disobedience, you ought not only to be exempt from punishment but even to have good done unto you. But if so, that absurdity will be found to result, which is in circulation with so many, that good comes of evil, and that evil is the cause of good; and one of the two is necessary, either that He be clearly unjust in punishing, or that if He punish not, it is from our vices that He has the victory. And both of these are absurd to a degree. And himself meaning to show this too, he introduces the Greeks (i.e. heathens) as the fathers of these opinions, thinking it enough to allege against what he has mentioned the character of the persons who say these things. For then they used to say in ridicule of us, “let us do evil that good may come.” And this is why he has stated it clearly in the following language.
Ver. 8. “If not (as some affirm that we say,) Let us do evil that good may come? Whose damnation is just.”
For whereas Paul said, “where sin abounded grace did much more abound”, in ridicule of him and perverting what he said to another meaning, they said, We must cling to vice that we may get what is good. But Paul said not so; however to correct this notion it is that he says, “What then? Shall we continue in sin that grace may abound? God forbid!” (ib. 6:1, 2.) For I said it, he means, of the times which are past, not that we should make this a practice. To lead them away then from this suspicion, he said, that henceforth this was even impossible. For “how shall we,” he says, “that are dead unto sin, live any longer therein?” Against the Greeks then he inveighs (κατέδραμεν) without difficulty. For their life was exceeding abandoned. But of the Jews, even if their life seemed to have been careless, still they had great means of cloaking these things in the Law and circumcision, and the fact of God having conversed with them, and their being the teachers of all. And this is why he strips them even of these, and shows that for these they were the more punished, and this is the conclusion to which he has here drawn his discussion. For if they be not punished, he would say, for so doing, that blasphemous language— let us do evil that good may come— must necessarily gain currency. But if this be impious, and they who hold this language shall be punished (for this he declared by saying, “whose damnation is just”), it is plain that they are punished. For if they who speak it be deserving of vengeance, much more are they who act it, but if deserving thereof, it is as having done sin. For it is not man that punishes them, that any one should suspect the sentence, but God, that does all things righteously. But if they are righteously punished, it is unrighteously that they, who make ridicule of us, said what they did. For God did and does everything, that our conversation might shine forth and be upright on every side.
Source: Homilies on Romans (New Advent)