John Chrysostom, on Rom 3:5

"But if our unrighteousness commend the righteousness of God, what shall we say? is God unrighteous Who taketh vengeance? I speak as a man. God forbid." 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; for after saying, "Is God unrighteous Who taketh 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 exceedeth, and has certain other unspeakable grounds for it.