'If a man finds it very hard to forgive injuries, let him look at a crucifix, and think that Christ has shed all His Blood for him, and not only forgave his enemies, but prayed the Eternal Father to forgive them also. Let him remember also that when he says the Pater Noster every day, instead of asking pardon for his sins, he is calling down vengeance upon them.'
St. Philip Neri
'Forgetting offences is a sign of sincere repentance. If you keep the memory of them, you may believe you have repented but you are like someone running in his sleep. Let no one consider it a minor defect, this darkness that often clouds the eyes even of spiritual people.'
St. John Climacus
'Saint John did not absolutely forbid that prayer should be made for those who "sin unto death," since he knew that Moses, Jeremiah, and Stephen had so prayed, and he himself implies that forgiveness is not to be denied them. Such intercessors, then, must be sought for after very grievous sins, for if any ordinary persons pray they are not heard. . . Stephen prayed for his persecutors, who had not been able even to listen to the Name of Christ, when he said of those very men by whom he was being stoned: "Lord, lay not this sin to their charge" And we see the result of this prayer in the case of the Apostle, for Paul, who kept the garments of those who were stoning Stephen, not long after became an apostle by the grace of God, having before been a persecutor.'
St. Ambrose of Milan
'There is a sin which is always "unto death" (1 John 5:16): the sin for which we do not repent. For this sin even a saint's prayers will not be heard.'
St. Mark the Ascetic
'He that seeketh to revenge himself, shall find vengeance from the Lord, and he will surely keep his sins in remembrance.
Forgive thy neighbour if he hath hurt thee: and then shall thy sins be forgiven to thee when thou prayest.
Man to man reserveth anger, and doth he seek remedy of God? He hath no mercy on a man like himself, and doth he entreat for his own sins? He that is but flesh, nourisheth anger, and doth he ask forgiveness of God? who shall obtain pardon for his sins?'
Ecclesiasticus 28:1-5