If any one saith, that, after the grace of Justification has been received, to every penitent sinner the guilt is remitted, and the debt of eternal punishment is blotted out in such wise, that there remains not any debt of temporal punishment to be discharged either in this world, or in the next in Purgatory, before the entrance to the kingdom of heaven can be opened (to him); let him be anathema.
Temporal penalties for sin are a stumbling block for some Protestants, but they really shouldn’t be. Our sins have consequences that aren’t strictly eternal, as David learned (when he was told that his son would die, although his sins were forgiven). The “Reformers” were wrong when they abandoned this doctrine.
In any case, neither Purgatory nor temporal punishment is contrary to the doctrine of justification by grace alone.