John Calvin Commentary Romans 5:20

"And the law came in besides, that the trespass might abound; but where sin abounded, grace did abound more exceedingly:" — Romans 5:20 (ASV)

But the law intervened, etc. This subject depends on what he had said previously: that there was sin before the law was published. This being the case, the following question immediately arises: For what purpose was the law given? It was therefore necessary to resolve this difficulty. However, as a longer digression was not appropriate, he deferred the subject and handled it in another place. Now, in passing, he only says that the law entered so that sin might abound, for he does not describe here the whole office and use of the law, but only touches on one part, which served his current purpose.

He indeed teaches us that it was necessary that people's ruin should be more fully revealed to them, so that a way might be opened for the favor of God. They were indeed shipwrecked before the law was given. However, as they seemed to themselves to be swimming while in their destruction, they were thrust down into the depths, so that their deliverance might appear more evident when they emerge from there beyond all human expectation. Nor was it unreasonable that the law should be partly introduced for this purpose—that it might again condemn those already condemned. For nothing is more reasonable than that people should, by all means, be brought, indeed forced, by being proven guilty, to know their own evils.

That offense might abound, etc. It is well known how some, following Augustine, usually explain this passage: that lust is irritated all the more while it is checked by the restraints of the law, for it is human nature to strive for what is forbidden.

But I understand no other increase to be intended here than that of knowledge and obstinacy. For sin is set by the law before people's eyes, so that they may be continually forced to see that condemnation is prepared for them. Thus sin disturbs the conscience, which people forget when they cast it behind them. And further, the one who previously only transgressed the bounds of justice now becomes, when the law is introduced, a despiser of God’s authority, since the will of God is made known to them, which they now wantonly trample underfoot. It follows from this that sin is increased by the law, since now the authority of the lawgiver is despised and his majesty degraded.

Grace has superabounded. After sin has held people sunk in ruin, grace then comes to their help. For he teaches us that the abundance of grace becomes more illustrious for this reason: that while sin is overflowing, grace pours itself forth so exuberantly that it not only overcomes the flood of sin but wholly absorbs it. And from this we may learn that our condemnation is not set before us in the law so that we may abide in it, but so that, having fully known our misery, we may be led to Christ, who is sent to be a physician to the sick, a deliverer to the captives, a comforter to the afflicted, and a defender to the oppressed (Isaiah 61:1).