Objection 1. It would seem that the saints in glory have not penance. For, as Gregory says (Moral. iv), "the blessed remember their sins, even as we, without grief, remember our griefs after we have been healed." But penance is grief of the heart. Therefore the saints in heaven have not penance.
Objection 2. Further, the saints in heaven are conformed to Christ. But there was no penance in Christ, since there was no faith which is the principle of penance. Therefore there will be no penance in the saints in heaven.
Objection 3. Further, a habit is useless if it is not reduced to its act. But the saints in heaven will not repent actually, because, if they did, there would be something in them against their wish. Therefore the habit of penance will not be in them.
Objection 4. On the other hand, penance is a part of justice. But justice is "perpetual and immortal" (Wisdom 1:15), and will remain in heaven. Therefore penance will also.
Objection 5. Further, we read in the Lives of the Fathers, that one of them said that even Abraham will repent of not having done more good. But one ought to repent of evil done more than of good left undone, and which one was not bound to do, for such is the good in question. Therefore repentance will be there of evil done.
I answer that, The cardinal virtues will remain in heaven, but only as regards the acts which they exercise in respect of their end. Wherefore, since the virtue of penance is a part of justice which is a cardinal virtue, whoever has the habit of penance in this life, will have it in the life to come: but he will not have the same act as now, but another, viz. thanksgiving to God for His mercy in pardoning his sins.
Reply to Objection 1. This argument proves that they do not have the same act as penance has now; and we grant this.
Reply to Objection 2. Christ could not sin, wherefore the matter of this virtue was lacking in His respect both actually and potentially: so that there is no comparison between Him and others.
Reply to Objection 3. Repentance, properly speaking, considered as that act of penance which is in this life, will not be in heaven: and yet the habit will not be without its use, for it will have another act.
Reply to Objections 4 and 5. We grant the Fourth argument. But since the Fifth Objection proves that there will be the same act of penance in heaven as now, we answer the latter by saying that in heaven one will be altogether conformed to the will of God. Wherefore, as God, by His antecedent will, but not by His consequent will, wishes that all things should be good, and therefore that there should be no evil, so is it with the blessed. It is this will that this holy father improperly calls penance.
Source: Summa Theologica (New Advent)