Augustine of Hippo
Catena Aurea · Johannesevangelium 18
And Simon Peter followed Jesus, and so did another disciple: that disciple was known unto the high priest, and went in with Jesus into the palace of the high priest. But Peter stood at the door without. Then went out that other disciple, which was known unto the high priest, and spake unto her that kept the door, and brought in Peter. Then saith the damsel that kept the door unto Peter, Art not thou also one of this man’s disciples? He saith, I am not. And the servants and officers stood there, who had made a fire of coals; for it was cold: and they warmed themselves: and Peter stood with them, and warmed himself.
(Tr. cxiii) But what wonder, if God foretold truly, man presumed falsely. Respecting this denial of Peter we should remark, that Christ is not only denied by him, who denies that He is Christ, but by him also who denies himself to be a Christian. For the Lord did not say to Peter, Thou shalt deny that thou art My disciple, but, Thou shalt deny Me. (Luke 22:34) He denied Him then, when he denied that he was His disciple. And what was this but to deny that he was a Christian? How many afterwards, even boys and girls, were able to despise death, confess Christ, and enter courageously into the kingdom of heaven; which he who received the keys of the kingdom, was now unable to do? Wherein we see the reason for His saying above, Let these go their way, for of those which Thou hast given Me, have I lost none. If Peter had gone out of this world immediately after denying Christ, He must have been lost.