Matthew 16:19

See how great power has that rock upon which the Church is built, that its sentences are to continue firm as though God gave sentence by it. Let him then be without blame who binds or looses another, that he may be found worthy to bind or loose in heaven. Moreover, to him who shall be able by his virtues to shut the gates of hell, are given in reward the keys of the kingdom of heaven. For every kind of virtue when any has begun to practise it, as it were opens itself before Him, the Lord, namely, opening it through His grace, so that the same virtue is found to be both the gate, and the key of the gate. But it may be that each virtue is itself the kingdom of heaven.

Then He mentions also another honor. "And I also will give thee the keys of the heavens." But what is this, "And I also will give thee?" "As the Father hath given thee to know me, so will I also give thee." And He said not, "I will entreat the Father" (although the manifestation of His authority was great, and the largeness of the gift unspeakable), but, "I will give thee." What dost Thou give? tell me. "The keys of the heavens, that whatsoever thou shalt bind on earth, shall be bound in Heaven, and whatsoever thou shalt loose on earth, shall be loosed in Heaven." How then is it not "His to give to sit on His right hand, and on His left," when He saith, "I will give thee"? Seest thou how He, His own self, leads Peter on to high thoughts of Him, and reveals Himself, and implies that He is Son of God by these two promises? For those things which are peculiar to God alone, (both to absolve sins, and to make the church incapable of overthrow in such assailing waves, and to exhibit a man that is a fisher more solid than any rock, while all the world is at war with him), these He promises Himself to give; as the Father, speaking to Jeremiah, said, He would make him as "a brazen pillar, and as a wall;" but him to one nation only, this man in every part of the world. I would fain inquire then of those who desire to lessen the dignity of the Son, which manner of gifts were greater, those which the Father gave to Peter, or those which the Son gave him? For the Father gave to Peter the revelation of the Son; but the Son gave him to sow that of the Father and that of Himself in every part of the world; and to a mortal man He entrusted the authority over all things in Heaven, giving him the keys; who extended the church to every part of the world, and declared it to be stronger than heaven. "For heaven and earth shall pass away, but my word shall not pass away." How then is He less, who hath given such gifts, hath effected such things? And these things I say, not dividing the works of Father and Son ("for all things are made by Him, and without Him was nothing made which was made"): but bridling the shameless tongue of them that dare so to speak. But see, throughout all, His authority: "I say unto thee, Thou art Peter; I will build the Church; I will give thee the keys of Heaven."

Bishops and Presbyters; not understanding this passage, assume to themselves something of the lofty pretensions of the Pharisees, and suppose that they may either condemn the innocent, or absolve the guilty; whereas what will be enquired into before the Lord will be not the sentence of the Priests, but the life of him that is being judged. We read in Leviticus of the lepers, how they are commanded to show themselves to the Priests, and if they have the leprosy, then they are made unclean by the Priest; not that the Priest makes them leprous and unclean, but that the Priest has knowledge of what is leprosy and what is not leprosy, and can discern who is clean, and who is unclean. In the same way then as there the Priest makes the leper unclean, here the Bishop or Presbyter binds or looses not those who are without sin, or guilt, but in discharge of his function when he has heard the varieties of their sins, he knows who is to be bound, and who loosed.

For as with a zeal beyond the others he had confessed the King of heaven, he is deservedly entrusted more than the others with the keys of the heavenly kingdom, that it might be clear to all, that without that confession and faith none ought to enter the kingdom of heaven. By the keys of the kingdom He means discernment and power; power, by which he binds and looses, discernment, by which he separates the worthy from the unworthy. But this power of binding and loosing, though it seems given by the Lord to Peter alone, is indeed given also to the other Apostles, and is even now in the^ Bishops and Presbyters in every Church. (vid. Matt. 18:18.) But Peter received in a special manner the keys of the kingdom of heaven, and a supremacy of judicial power, that all the faithful throughout the world might understand that all who in any manner separate themselves from the unity of the faith, or from communion with him, such should neither be able to be loosed from the bonds of sin, nor to enter the gate of the heavenly kingdom.

(interlin.) It follows, And whatsoever thou shalt bind; that is, whomsoever thou shalt judge unworthy of forgiveness while he lives, shall be judged unworthy with God; and whatsoever thou shalt loose, that is, whomsoever thou shalt judge worthy to be forgiven while he lives, shall obtain forgiveness of his sins from God. (ap. Anselm.) This power was committed specially to Peter, that we might thereby be invited to unity. For He therefore appointed him the head of the Apostles, that the Church might have one principal Vicar of Christ, to whom the different members of the Church should have recourse, if ever they should have dissensions among them. But if there were many heads in the Church, the bond of unity would be broken. Some say that the words upon earth denote that power was not given to men to bind and loose the dead, but the living; for he who should loose the dead would do this not upon earth, but after the earth.