We pass forgiveness on to others because the Lord in grace did not demand justice for our infractions, but out of love, and for the relationship He desired with us, freely forgave. Those who have sinned must be patient with sinners. Those who have been forgiven need to find ways to forgive. Forgiveness of others is gratitude to our Father who forgave us. Forgiving another thus becomes an act of worship.
“Then his master, after he had called him, said to him, ‘You wicked servant! I forgave you all that debt because you begged me. Should you not also have had compassion on your fellow servant, just as I had pity on you?’” Matthew 18:32-33 (NKJV)