I don't understand how the forgiveness that we give to others in the Fifth Petition differs from the forgiveness that we withhold from the impenitent in the use of the Keys. The (Kuske) Catechism describes the forgiveness of the Fifth Petition as including "anyone who sins against us," and again as "all who sin against us." In response to a similar question asked earlier, Q & A did not agree with the unconditional forgiveness that writer thought necessary. When does the impenitence of "those who trespass against us" become the deciding factor in whom we forgive? Does the new Catechism clarify this in its discussion of the Fifth Petition? Thank you!
The context of questions is always important, and that context is often missing from questions that are submitted. When there are questions about forgiving others, we need to keep a number of things in mind.
If a person has sinned against us and is impenitent, we exhibit our Christian faith by harboring no grudges or ill will against that person. We have the privilege of telling the person we personally forgive him or her for the sin committed, but we want the individual to know that God’s forgiveness is so much more important than the forgiveness we express. Repentance, of course, is paramount to enjoying forgiveness from God.
An answer to a similar question in Forward in Christ proposed this example of a conversation to an impenitent sinner: “I fully and freely forgive you, sinner to sinner. I hold no grudge against you, seek no retaliation, and will keep no record of wrongs. I have no desire or need for this. My Lord Jesus is my ultimate Protector and he will satisfy justice in the end. Vengeance is his to give, not mine. But please understand that this may really mean very little for your long-term well-being. If and as long as you do not repent before God of your sin, you do not enjoy the forgiveness Christ earned for you. You forfeit personal benefit of his pardon. That is the forgiveness I seek for you but cannot give or announce to you at this time. That is the forgiveness you need most of all. You have my forgiveness, given cheerfully in love. But just like me, a sinner like you, you need the personal enjoyment of Christ’s forgiveness, which is also freely given. I am willing to do anything I can to help you enjoy this.”
Even when Christians represent God and, out of concern for the sins and impenitence of others, exercise the “binding key” and retain the sins of the impenitent (John 20:23), they seek to display a Christ-like love to others and avoid any personal animosity towards those who have sinned against them and remain impenitent.