Christ is Risen, Alleluia
Now according to Father Ambrose, a sin can be forgiven after death. How can a mortal sin be forgiven after death if that person has been condemned to everlasting fire?
How? Because Eastern Christians, Orthodox and Byzantine Catholic, believe there is a possibility of salvation right up until the time of the final judgement when Christ shall return with all the angels to judge the earth.
Your Church teaches that what it calls venial sins may be forgiven after death... but it draws back from saying the same of what it calls mortal sins. The East makes no such clearcut distinction between sins, apart from the obvious fact that some are worse than others.
An interesting quote from Saint Martin of Tours which backs up Saint Augustine's statement that in the early Church there was a widespread belief in the possibility of final salvation for all, even including for the devil if he repented.“If thou, thyself, wretched being, wouldst but desist from attacking mankind, and even, at this period, when the day of judgment is at hand, wouldst only repent of your deeds, I, with a true confidence in the Lord, would promise you the mercy of Christ.
Martin preaches Repentance even to the Devil.
Now, the devil, while he tried to impose upon the holy man by a thousand injurious arts, often thrust himself upon him in a visible form, but in very various shapes. For sometimes he presented himself to his view changed into the person of Jupiter, often into that of Mercury and Minerva. Often, too, were heard words of reproach, in which the crowd of demons assailed Martin with scurrilous expressions. But knowing that all were false and groundless, he was not affected by the charges brought against him. Moreover, some of the brethren bore witness that they had heard a demon reproaching Martin in abusive terms, and asking why he had taken back, on their subsequent repentance, certain of the brethren who had, some time previously, lost their baptism by falling into various errors. The demon set forth the crimes of each of them; but they added that Martin, resisting the devil firmly, answered him, that by-past sins are cleansed away by the leading of a better life, and that through the mercy of God, those are to be absolved from their sins who have given up their evil ways. The devil saying in opposition to this that such guilty men as those referred to did not come within the pale of pardon, and that no mercy was extended by the Lord to those who had once fallen away, Martin is said to have cried out in words to the following effect: “If thou, thyself, wretched being, wouldst but desist from attacking mankind, and even, at this period, when the day of judgment is at hand, wouldst only repent of your deeds, I, with a true confidence in the Lord, would promise you the mercy of Christ.”
O what a holy boldness with respect to the loving-kindness of the Lord, in which, although he could not assert authority, he nevertheless showed the feelings dwelling within him! And since our discourse has here sprung up concerning the devil and his devices, it does not seem away from the point, although the matter does not bear immediately upon Martin, to relate what took place; both because the virtues of Martin do, to some extent, appear in the transaction, and the incident, which was worthy of a miracle, will properly be put on record, with the view of furnishing a caution, should anything of a similar character subsequently occur.
Source :: Sulpitius Severus "On the Life of St. Martin" Chapter XXI