What “revelation” tells us how we receive indulgences?
The granting of indulgences is a part of Church’s life that is closely linked to the Sacrament of Reconciliation and the forgiveness of sins. The proper
authority of the Church to grant indulgences (insofar as this question asks for a “revelation” on these matters) can be drawn from Jesus’ act of giving the
apostles (and thereby, the Church) the power of binding and loosing, as given first to Peter as recorded in Matthew 16:19 and later to all of the apostles in Matthew 18:18 – a power which has to do with forgiveness of sin.
According to the Catechism, which takes its explanation from the apostolic constitution of Pope Paul VI entitled The Doctrine of Indulgences, an indulgence is the removal of the temporal (earthly) punishment due to sins. Note that this removal of punishment is accomplished by God, is granted when one’s sins have already been forgiven, and is completed when the person who seeks such removal of punishment fulfills certain prescribed conditions. This removal of temporal punishment is given through the Church, who has been given by Christ the authority to forgive sins. There are two types of indulgences stated here, partial (removing of some of this temporal punishment) and plenary (removing of all temporal punishment).
In considering “how” we receive an indulgence, it is important to realize that indulgences must be received according to the right intention and with a right disposition toward God and His grace if the desired effect is to be truly received. As it is God who truly accomplishes forgiveness and removal of punishments, we are primarily called to be receptive and humble in our desire to receive these gifts of grace. While an indulgence may appear at face value as nothing more than a “get out of jail free card,” the truth is that the benefit of an indulgence is only received when one receives it with a humble disposition of faith and in accord with the acts of prayer and/or piety that are to accompany it. If one seeks an indulgence with faith and the requisites of prayer, the acknowledgement of sin (in confession with valid absolution), the worthy reception of Holy Communion, etc., the benefit of the indulgence will more fruitfully be received than one who may look to receive the indulgence presuming that once they “have it,” all will be well without regard to whether or not they repent of sin and worship God rightly or not.
Thus, indulgences truly are a gift of grace that is entrusted to the Church as a participation in the ministry of forgiveness and reconciliation. Our right reception of them is founded upon the power to bind and loose that Jesus gave to the apostles and requires our own humble faith that God’s grace may be effective in us.