Romans 5:20–21:

…but where sin increased, grace abounded all the more, so that, as sin reigned in death, grace also might reign through righteousness leading to eternal life through Jesus Christ our Lord.

Martyn Lloyd-Jones, Romans: Assurance (Banner of Truth, 1971), pages 299–300:

What grace has done is not merely to counteract exactly what sin has done. If grace had done that, and that alone, it would still be something wonderful. If the effect of grace had merely been to wipe out, and to cancel, all that had happened on the other side, we should have had a theme for praising God sufficient to last us through all eternity.

But, says the Apostle, it is not an exact counterbalance; what I have on the right side does not exactly tally with that I have on the left. In fact there is no comparison; it is a superfluity, an abounding, and engulfing, it is an overflowing on the side of grace. We must hold on to this truth at all costs and get it clear in our minds. The point is that grace does not merely exactly balance, it does not just undo what sin has done; it does much more.