Forgive us our debts
Whether forgiveness is conditioned on forgiving, standing beside salvation by grace.
Matthew 6:9-15
9Pray like this: ‘Our Father in heaven, may your name be kept holy.
10Let your Kingdom come. Let your will be done on earth as it is in heaven.
11Give us today our daily bread.
12Forgive us our debts, as we also forgive our debtors.
13Bring us not into temptation, but deliver us from the evil one. For yours is the Kingdom, the power, and the glory forever. Amen.’
14“For if you forgive men their trespasses, your heavenly Father will also forgive you.
15But if you don’t forgive men their trespasses, neither will your Father forgive your trespasses.
What each tradition says
Rabbinic / Midrashic
Ben Sira says: forgive thy neighbor the hurt he hath done unto thee, so shall thy sins also be forgiven when thou prayest. On this teaching, a person's own sins are forgiven at prayer in the measure that the hurt done by a neighbor has been forgiven.
The Jewish Encyclopedia (1905), The Jewish Encyclopedia (1905), art. "Lord's Prayer, The" — On the forgiveness petition and its Jewish parallels
Patristic
Augustine holds that we must confess that all sins committed against us are to be forgiven. This is required if we wish our Father to forgive the sins we commit against Him.
Augustine, Our Lord's Sermon on the Mount, Book II (Nicene and Post-Nicene Fathers, First Series, Vol. 6) — Book II, §29 (on the fifth petition)
Catholic
Chrysostom says God puts our judgment in our own hands, so none can complain, since each is the author of his own sentence. He could have forgiven our sins without this condition, but consulted our good by giving us opportunities to practice daily piety and mildness.
George Leo Haydock, George Haydock's Catholic Bible Commentary (1859) — On Matthew 6:12
Orthodox
Chrysostom says that the beginning is of us. He also says that we ourselves have control over the judgment that is to be passed upon us.
John Chrysostom, Homilies on the Gospel of Saint Matthew (Nicene and Post-Nicene Fathers, First Series, Vol. 10) — Homily XIX, on Matthew 6:9-15 (the fifth petition)
Reformed / Protestant
Calvin says this condition is added so that no one who is not pure and free from all resentment may presume to ask God for forgiveness. Yet the forgiveness we ask from God does not depend on the forgiveness we grant others. Christ's design was to exhort us to forgive offenses and to ratify our confidence in our own forgiveness.
John Calvin, Commentary on Matthew, Mark, Luke — Volume 1 (Calvin Translation Society) — On Matthew 6:12
Evangelical
Wesley reads this petition as asking the Lord to give redemption in his blood and the forgiveness of sins. As the Lord enables us freely and fully to forgive every person, so the petition asks him to forgive all our trespasses.
John Wesley, Wesley's Notes on the Bible (Notes on the Gospel According to St Matthew) — Note on Matthew 6:12