Origen
Catena Aurea · Matthäusevangelium 16
When Jesus came into the coasts of Cæsarea Philippi, he asked his disciples, saying, Whom do men say that I the Son of man am? And they said, Some say that thou art John the Baptist; some, Elias; and others, Jeremias, or one of the prophets. He saith unto them, But whom say ye that I am? And Simon Peter answered and said, Thou art the Christ, the Son of the living God. And Jesus answered and said unto him, Blessed art thou, Simon Barjona: for flesh and blood hath not revealed it unto thee, but my Father which is in heaven. And I say also unto thee, That thou art Peter, and upon this rock I will build my Church: and the gates of hell shall not prevail against it. And I will give unto thee the keys of the kingdom of heaven: and whatsoever thou shalt bind on earth shall be bound in heaven: and whatsoever thou shalt loose on earth shall be loosed in heaven.
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.