Thomas Aquinas, on Rom 3:5

“But if our injustice commend the justice of God, what shall we say? Is God unjust, who executeth wrath?”

“Then when he says, but if our wickedness, he excludes a false understanding of the text he cited. For someone might understand these words according to the sense that that would be taken in a causal, not a consecutive, sense. Then it would follow that man's sin would be directly ordained to commend God's justice. But the Apostle shows that this is false. Hence he says that that is used consecutively, on the ground that David sinned and then the manifestation of divine justice followed, but not causally, as if a man's sin commended God's justice. He proves this by showing that it leads to something unfitting in two ways: first, on the part of divine judgment; second, on the part of human judgment. In regard to the first he does three things: first, he presents the false sense; second, he shows that something unfitting follows from this, at what shall we say? Is God unjust; third, he shows that it is unfitting, at God forbid! It should be noted that above the Apostle had made two comparisons; in the first he compared divine truth to human falsity when he said: but God is true and every man a liar; in the second, God's justice to human sin, in the words of a psalm, where it is said: against you, you only, have I sinned (Ps 51:4), that you may be justified. In regard to the first comparison he says: if these words are taken to mean that our iniquity directly commends God's justice, what shall we say? In other words, we could not accept the unfittingness that follows. For sin is not necessary for God to have his justice commended: he does not desire a multitude of faithless and useless children (Sir 16:1). He expresses the unfittingness that follows, when he says: is God unjust, who executes wrath, i.e., vengeance for sin. For this follows from the supposition. For if sin were directly ordained to commending justice, it would not be deserving of punishment but of reward. Consequently, God would be unjust in punishing men for sin, contrary to what is stated in Deuteronomy: God is faithful and without iniquity (Deut 32:4).”

Imported from an open dataset — not yet checked against the printed edition.