How do we know the doctrine of forgiveness is true?

The assurance of forgiveness is fundamentally grounded in the sacrifice of Christ, as articulated in Ephesians 1:7, where Paul states that we have redemption through His blood, resulting in the forgiveness of sins. This forgiveness is described as a gift that flows from the 'riches of His grace,' emphasizing that it is not earned by human effort or righteousness. Paul reiterates this throughout his letters, consistently pointing to Christ's work as the basis for forgiveness. Forgiveness is presented as a vital aspect of the gospel, where Christ's death and resurrection provide a pathway for reconciliation with God, confirming the truth of this doctrine to all who believe.