Forgive us our Trespasses - Parable of the Merciless Servant

The parable of the merciless servant illustrates the meaning of  "forgive us our trespasses as we forgive those who trespass against us," a petition included in the Lord's Prayer.  Anger can be righteous, but when we let it harden into resentment it becomes a poison that blocks the grace of God from flowing into us and through us. Forgiveness removes the block.