Adam Clarke on Romans 3:8

Apostle. And not rather, etc. - And why do you not say, seeing you assume this ground, that in all cases we should do wickedly, because God, by freely pardoning, can so glorify his own grace? This is a most impious sentiment, but it follows from your reasoning; it has, indeed, been most injuriously laid to the charge of us apostles, who preach the doctrine of free pardon, through faith, without the merit of works; but this is so manifest a perversion of the truth that a just punishment may be expected to fall on the propagators of such a slander.