How do we know Jesus' ability to forgive sins is true?

Throughout the Gospels, Jesus demonstrates His power through miracles and authoritative teachings, verifying His claim to forgive sins. In Mark 2, He not only forgives the sins of a sick man but also heals him as a physical sign of spiritual healing. This action reveals that His authority to forgive is grounded in His divinity as the Son of Man, providing assurance to believers of the reality of forgiveness. This truth points to the grace that God extends to sinners who cannot save themselves.