From Pope St. John Paul II’s Apostolic Exhortation Reconciliatio et Pænitentia (1984):
The other essential stage of the sacrament of penance at this time belongs to the confessor as judge and healer, a figure of God the Father welcoming and forgiving the one who returns: This is the absolution. The words which express it and the gestures that accompany it in the old and in the new Rite of Penance are significantly simple in their grandeur. The sacramental formula “I absolve you” and the imposition of the hand and the Sign of the Cross made over the penitent show that at this moment the contrite and converted sinner comes into contact with the power and mercy of God. It is the moment at which, in response to the penitent, the Trinity becomes present in order to blot out sin and restore innocence. And the saving power of the passion, death and resurrection of Jesus is also imparted to the penitent as the “mercy stronger than sin and offense,” as I defined it in my encyclical Dives in Misericordia. God is always the one who is principally offended by sin—”Tibi soli peccavi!”—and God alone can forgive. Hence the absolution that the priest, the minister of forgiveness, though himself a sinner, grants to the penitent is the effective sign of the intervention of the Father in every absolution and the sign of the “resurrection” from “spiritual death” which is renewed each time that the sacrament of penance is administered. Only faith can give us certainty that at that moment every sin is forgiven and blotted out by the mysterious intervention of the Savior.
Satisfaction is the final act which crowns the sacramental sign of penance. In some countries the act which the forgiven and absolved penitent agrees to perform after receiving absolution is called precisely the penance. What is the meaning of this satisfaction that one makes or the penance that one performs? Certainly it is not a price that one pays for the sin absolved and for the forgiveness obtained: No human price can match what is obtained, which is the fruit of Christ’s precious blood. Acts of satisfaction—which, while remaining simple and humble, should be made to express more clearly all that they signify—mean a number of valuable things: They are the sign of the personal commitment that the Christian has made to God in the sacrament to begin a new life (and therefore they should not be reduced to mere formulas to be recited, but should consist of acts of worship, charity, mercy or reparation). They include the idea that the pardoned sinner is able to join his own physical and spiritual mortification—which has been sought after or at least accepted—to the passion of Jesus, who has obtained the forgiveness for him. They remind us that even after absolution there remains in the Christian a dark area due to the wound of sin, to the imperfection of love in repentance, to the weakening of the spiritual faculties. It is an area in which there still operates an infectious source of sin which must always be fought with mortification and penance. This is the meaning of the humble but sincere act of satisfaction.189
189 I dealt with this subject concisely at the general audience of March 7, 1984: Insegnamenti VII, 1 (1984), 631-633.
— Reconciliatio et Pænitentia 31