Adam Clarke on Romans 3:5

Jew. But if our unrighteousness commend the righteousness of God - May we not suppose that our unrighteousness may serve to commend and illustrate the mercy of God in keeping and fulfilling to us the promise which he made to our forefathers? The more wicked we are, the more his faithfulness to his ancient promise is to be admired. And if so, would not God appear unjust in taking vengeance and casting us off?

I speak as a man - I feel for the situation both of myself and my countrymen, and it is natural for one to speak as I do.