The fifth petition. "Forgive us our trespasses as we forgive those who trespass against us."
Say: "O dear Lord, God and Father, enter not into judgment against us because no man living is justified before You. Do not count it against us as a sin that we are so unthankful for thine ineffable goodness, spiritual and physical, or that we stray into sin many times every day, more often than we can know or recognize. Do not look upon how good or how wicked we have been but only upon the infinite compassion which You have bestowed upon us in Christ, Your dear Son.
Grant forgiveness also to those who have harmed or wronged us, as we forgive them from our hearts. They inflict the greatest injury upon themselves by arousing Your anger in their actions toward us. We are not helped by their ruin; we would much rather that they be saved with us. Amen."
(Anyone who feels unable to forgive, let him ask for grace so that he can forgive; but that belongs in a sermon.)
(‘A Simple Way To Pray by Martin Luther’: Prayer, the Lord's Prayer, the 10 Commandments, and the Creed - A Letter to His Barber, Master Peter Beskendorf, Spring 1535. The ebook or PDF is widely available to download for free online.)