Rise and Walk
The verb forgive in verse 21 translates the Greek aphiemi as "release, to set free, to let free, to remit, to discharge, to condone."
To forgive is to let go, to set free, to condone, to relieve from the weight of guilt and of wrong-doing. To forgive is not an action of the mind, nor is it an action of the will: it is a definite choice of the soul to follow the way of love, whatever that may cost. To forgive is the definite choice to not dwell upon the evil that one has been subjected to or on the harm inflicted. To forgive is to let go out of love, not out of anger. Letting go permits one to rise and to walk. Dwelling on evil leads in any case to evil and paralyzes the mind, the soul, and the body.
Jesus forgives because he is the only one who can do so. To forgive is not a human action, not even the most elevated human spirit is capable of forgiving. No man shut up tight within himself can, with human strength alone, ask for forgiveness and receive mercy. The Word of Jesus that concedes forgiveness is an all powerful word which commands abolition of the error and of the sin committed. The human heart that forgives by the gift of the Paraclete is fruit of the same divine omnipotence that commands and orders that the error and the harm received be abolished. In the same way, the tears of a contrite heart which humbly begs for forgiveness from God the Paraclete is an action coming from the omnipotence of God. It is God, it is Jesus who in his mercy by first forgiving His children always, establishes the absolute power and omnipotence of forgiveness offered and requested.
This the the true prodigy. The prodigious things that Jesus does make people tremble and glorify God, but the real miracle is divine forgiveness which, engendered by a man's humble but powerful faith, heals and regenerates all of man.