The Catechism of the Summa - Tertia Pars - XL. OF THE MINISTER OF THE SACRAMENT OF PENANCE, AND OF THE POWER OF THE KEYS: OF ABSOLUTION; OF INDULGENCES; OF THE COMMUNION OF SAINTS; AND OF EXCOMMUNICATION (A)

(A)
What is meant by the power of the keys?

It is nothing more than that power which opens the gate of heaven by removing an obstacle which prevents entrance thereto, namely sin and the punishment due to sin (XVII. 1).

Where is this power?

First of all it is in the Holy Trinity as in its primary source; then in the sacred humanity of Jesus Christ, by the merit of whose Passion the twofold obstacle above mentioned was removed, and which also by its own power removes this obstacle; also because the efficacy of the Passion of Jesus Christ lives in the sacraments, which are channels, as it were, of His grace by which men participate in all its merits. It follows then that the ministers of the Church, who are the dispensers of the sacraments, have also the power of the keys which they have received from Christ Himself (XVII. 1).

Next - The Catechism of the Summa - Tertia Pars - XL. OF THE MINISTER OF THE SACRAMENT OF PENANCE, AND OF THE POWER OF THE KEYS: OF ABSOLUTION; OF INDULGENCES; OF THE COMMUNION OF SAINTS; AND OF EXCOMMUNICATION (B)