But if our unrighteousness serves to show the righteousness of God, what shall we say? That God is unrighteous to inflict wrath on us? (I speak in a human way.) By no means! For then how could God judge the world? -Romans 3:5–6
Paul, speaking on behalf of his interlocutor, raises the objection that if the main result of man’s sin is that it advances God’s purpose in the world, then doesn’t it seem that God is unjust for punishing sin? Sin is simply giving God the opportunity to display his righteousness.
Therefore it is unjust to punish sinners who are simply advancing his agenda.
Cue the emphatic repudiation: by no means!
It is not the sin that gives God the opportunity to reveal his righteousness. It’s God’s providential way of dealing with sin that provides the opportunity for his righteousness to be revealed.
Otherwise, how could he judge the world justly—and be just himself—if he simply let the sinner go free?
Question: how would we view an earthly judge who let criminals go free because, as he might reason, their crimes gave him job security?