9 Hath your neighbour wronged and grieved you, and involved you in a thousand ills? Be it so, yet do not prosecute vengeance on your own part, lest you do desire to your Lord! Yield the matter to God, and He will dispose of it much better than you can desire. To you He has given charge simply to pray for the injurer; but how to deal with him, He has ordered you to leave to Himself. Never can you so avenge yourself, as He is prepared to avenge you, if you give place to Him alone, and dost not utter imprecations on him who has aggrieved you; but sufferest God to be sole arbiter of the sentence.
For although we may pardon those who have aggrieved us; although we may be reconciled; although we may pray for them; yet God does not pardon, unless they themselves are converted, and become better. And He withholds pardon, with a view to their own advantage. For He praises you, and approves you for your spiritual wisdom; but visits him, in order that he may not grow worse by your wisdom. So that the common saying on this subject is not to the point. For many there are, who when I reproach them because after being exhorted to be reconciled to their enemies, they will not be persuaded to it, think fit to proffer this apology, which is nothing less than a cloak for their iniquity.
“I am unwilling,” says one, “to be reconciled, lest I should make the man worse, more ill-tempered, and more disposed to treat me contemptuously hereafter.” Besides this, they also make this plea: “Many people,” say they, “think it is weakness in me to come first to a reconciliation, and to entreat my enemy.” All these things are foolish; for the Eye that slumbers not has seen your good intention; wherefore, it behooves you to make no account of the opinion of your fellow-servants, when you have gained the opinion of the Judge, Who is about to try your cause.
Source: Homilies on the Statues (New Advent)