Concerning the Nature of Good, Against the Manichæans 9
9 Punishment is Constituted for the Sinning Nature that It May Be Rightly Ordered PL 42, 554
What sort of punishment, and how great, is due to each fault, belongs to Divine judgment, not to human; which punishment assuredly when it is remitted in the case of the converted, there is great goodness on the part of God, and when it is deservedly inflicted, there is no injustice on the part of God; because nature is better ordered by justly smarting under punishment than by rejoicing with impunity in sin; which nature nevertheless, even thus having some measure, form, and order, in whatever extremity there is as yet some good, which things, if they were absolutely taken away, and utterly consumed, there will be accordingly no good, because no nature will remain.
Poena peccanti naturae, ut recte ordinetur, constituta. Qualis autem et quanta poena cuique culpae debeatur, divini judicii est, non humani: quae utique et cum conversis remittitur, magna est bonitas apud Deum; et cum debita redditur, nulla est iniquitas apud Deum: quia melius ordinatur natura, ut juste doleat in supplicio, quam ut impune gaudeat in peccato. Quae tamen etiam sic habens nonnullum modum et speciem et ordinem, in quacumque extremitate adhuc aliquod bonum est: quae si omnino detrahantur, ei penitus consumantur, ideo nullum bonum erit, quia nulla natura remanebit.