The sermon centers on the radical, unconditional nature of Christian forgiveness, illustrated through Jesus' parable of the unforgiving servant in Matthew 18 and reinforced by the Heidelberg Catechism's fifth petition. It emphasizes that true forgiveness flows not from human effort or moral calculation, but from the profound mercy received through Christ, who has canceled our immense debt of sin. The parable exposes the hypocrisy of a servant who, having been forgiven a staggering debt, refuses to extend even a small measure of mercy to a fellow servant, revealing that genuine forgiveness is not optional but essential to the Christian life. The king's righteous rebuke underscores that withholding forgiveness from others, despite having been freely forgiven by God, is not merely a moral failing but a spiritual rebellion with eternal consequences. Ultimately, the sermon calls believers to live as living evidence of God's grace—forgiving others from the heart, not as a transaction, but as a response to the overwhelming mercy they have already received through Christ's blood.