Islam Commands The Faithful to be Forgiving, Always

One important sign of compassion is a person's ability to forgive. In Verse 7:199, God calls upon His servants to "make allowances for people, command what is right, and turn away from the ignorant."
Some may find this attitude difficult, but in the sight of God, it will be well rewarded. Those caught up in anger may well refuse to forgive mistakes. But to the faithful, God has revealed that it is better to forgive and, in Verse 26:40, has recommended this morality:

The repayment of a bad action is one equivalent to it. But if someone pardons and puts things right, his reward is with God...

In another verse (26:43), God reveals, "But if someone is steadfast and forgives, that is the most resolute course to follow." Verse 24:22 emphasizes that this is a very superior form of morality:
Those of you possessing affluence and ample wealth should not make oaths that they will not give to their relatives and the very poor and those who have emigrated in the way of God. They should rather pardon and overlook. Would you not love God to forgive you? God is Ever-Forgiving, Most Merciful."
In these words, He encourages the faithful to consider their own positions when it comes to forgiveness. Because everyone wants God to forgive him, to protect and show him mercy, so do we hope that all others will excuse and forgive our mistakes. Therefore, God has commanded the faithful to treat others in the same way they would like to be treated themselves. That important responsibility encourages the faithful to be forgiving towards one another. Our Prophet (may God bless him and grant him peace) encouraged them in these words: "That person is nearest to God, who pardons, when he has someone in his power, one who would have injured him."20
Believers, knowing that at any moment they may make a mistake, behave tolerantly towards others. Those verses in the Qur'an dealing with repentance make it clear that never making mistakes isn't as important as the determination never to repeat them. One of these verses (4:17) reads:

God accepts only the repentance of those who do evil in ignorance and then quickly repent after doing it. God turns towards such people. God is All-Knowing, All-Wise.

Under conditions that reveal an individual's sincerity, the faithful behave forgivingly and compassionately towards one another. If he who has committed error sincerely repents having done so, they cannot judge him for his past deeds. Even when the faithful are totally in the right and the other completely in the wrong, still they have no compunction about forgiveness, because God recommends such behavior as an example of proper morality (3:134):

Those who give in times of both ease and hardship, those who control their rage and pardon other people--God loves the good-doers.
When it comes to forgiving, the faithful don't distinguish between great and small errors, nor do they tailor their view of forgiveness accordingly. Someone may have committed an error inflicting severe harm on others, great financial loss, even loss of life. Yet the faithful know everything happens by the permission of God, as part of His destiny. When it comes to such things, they therefore place themselves in the hands of God and feel no personal anger.
Alternatively, if someone transgresses this Qur'anic rule and exceeds the bounds set by God, only God can judge that person's behavior. It is never up to the faithful to judge--or refuse to forgive--anyone on any matter. The truly sorry and repentant person will have his reward only in the sight of God. In many verses, God has revealed that apart from "associating partners to Him," He will forgive the errors of the faithful who repent sincerely. Since one man cannot know another's repentance, the faithful simply forgive in the manner God revealed to them. If the Qur'an has anything to say on a particular subject, they treat the person who has committed error in that light.