Romans 6:1
1What shall we say then? Shall we continue in sin, that grace may abound?
Wesley: the apostle here more fully vindicates his doctrine from the consequence suggested at Romans 3:7–8. He had then only denied and renounced it; here he removes the very foundation. The slander is that abundant grace makes continuing in sin reasonable.
One hears a pastoral danger, not a hypothetical only one camp must answer. Grace that abounds is not a license. The question will be met by baptismal union and a walk that must actually be taken—not by treating holiness as automatic in the justified.
Calvin: those who imagine that gratuitous righteousness is given apart from newness of life shamefully rend Christ asunder. The flesh, hearing of justification by faith, invents this slander: if grace abounds where sin abounds, then sink into sin to find more grace.
The objection is madness because Christ is the repairer of our righteousness. Medicine does not feed the disease it destroys. Justification never arrives without regeneration; the two are not separable gifts one might take and one refuse.
Key contrast Arminian readings typically read the question as a live temptation under grace: abundant mercy must not be twisted into license, and the baptized must actually refuse to continue. Reformed readings typically take it as a slander that rends Christ: gratuitous righteousness is never given apart from newness of life, so continuing in sin is not an option the regenerate might still reasonably choose.