Pope John Paul II the Great meets and forgives his would-be assassin, Turkish terrorist Mehmet Ali Acga, on 27 December 1983
From posts on the CHNI forum. David W. Emery is a fellow moderator over there. His words will be in blue (slightly edited in parts -- a few words omitted, and some parts compressed -- for the purpose of this post).
* * * * *Ask yourself how God forgives. What does he require for reconciliation when you have offended him? Repentance, right? No repentance, no forgiveness. Otherwise you would be free to sin with impunity. The same applies between human beings. If your brother sins against you, and you forgive him without his repentance, you are giving him license to continue sinning and offending. You become a doormat. God doesn’t allow that; neither should you. Repentance is required. Forgiveness is required when there is repentance. But not without it. The Lord’s Prayer says, “Forgive us our trespasses as we forgive those who trespass against us.” We are asking God’s forgiveness, and the condition of that forgiveness is that we forgive as God forgives. In other words, we first need to repent of our sins so that God can forgive us. And likewise, those who have offended us need to repent so that we can forgive them. As God forgives, so we also forgive, that his forgiveness may be fruitful in us and our forgiveness may be fruitful in others.
The Catholic always keeps in mind the sacramental forgiveness in confession, that requires remorse (contrition) or else it is null and void from the outset. There is also a biblical sense of what might be called "transactional forgiveness": a person repents, (preferably) does restitution of some sort, and is forgiven. God Himself won’t forgive us and grant us salvation if it isn’t preceded by our repentance, as David already noted. He doesn't simply declare us saved without our consent, including repentance. But He is always willing to forgive. His love and blessings towards us never end unless we reject Him.
It is very important, however, to note that there is such a thing “willingness to forgive” or “a forgiving spirit / heart,” or mercy, etc. This gets back to "Sermon on the Mount spirituality." What is in our heart will set the stage for how we act and react in real life situations. We have to be willing to forgive and to not become bitter, and to exercise a profound love and charity towards other people. Then when the opportunity comes to forgive someone who comes to us and repents of a sin done towards us (the full, Catholic sense of forgiveness described above), we are already prepared, as opposed to showing vengefulness and lack of charity and mercy.
I would prefer to separate “forgiveness” from “release.” To me they are really two different acts. I think this is what Dave is saying as well. When I forgive someone, I reconcile with him mutually. When I release someone, I am doing so unilaterally. A unilateral “forgiveness” or release is good, even necessary at times for us to get on with our lives. But while it can bring needed healing to the person offended, it cannot bring forgiveness to the unrepentant offender.
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Oftentimes, apologizing for an offense which was perceived, even if not actually committed, is a tactful way to restore the peace. It is an expedient allowing the other person to be “right” even though wrong; it involves a certain meekness on the part of the person actually wronged. Compare Ephesians 4:1–3: “I therefore, a prisoner for the Lord, beg you to lead a life worthy of the calling to which you have been called, with all lowliness and meekness, with patience, forbearing one another in love, eager to maintain the unity of the Spirit in the bond of peace.” Again, from the standpoint of the Beatitudes (Matthew 5:9): “Blessed are the peacemakers, for they shall be called sons of God.”
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In common parlance we do have a tendency to refer to both circumstances as “forgiveness.” It is for this reason that I needed to make the distinction, regardless of the words one might use, so that we could understand the dynamics. My point was that forgiveness remains unilateral until the offender repents. I may offer my forgiveness, but it has to be received and properly responded to before reconciliation can take place. This is what Dave cites as “willingness to forgive.” Withholding forgiveness, as you saw from the passage from the Matthew’s Gospel above, is always condemned; we must always be willing to forgive, even if the offender does not repent, just as God eternally stands ready to forgive as soon as we repent.