Then said the girl that kept the door unto Peter, Are not you also one of this man's disciples? He said, I am not.
Read Chapter 18
Cyril of Alexandria
As Christ had already foretold to Peter that he would thrice deny our Saviour Christ, and that before the cock crew his faith would fail, the inspired Evangelist relates in detail where, and how, the prophecy was fulfilled. The maid, seated at the door, then, inquires of him whether he was not one of the number of the disciples of Him Who was undergoing the unjust trial. Peter denies it, and parries the question as though it were a charge, saying, "I am not;" not fearing at all to be taken, or shrinking from proclaiming the truth, but disregarding and making light of enduring any kind of evil against his will in comparison with being with Christ. His transgression, then, proceeds from love, and his denial has its root in the love of God; not indeed proceeding from any just reasoning, but, at any rate, testifying to the fervour of his desire to be with Christ.
St. John gives here Peter's first denial, which is reunited to the other two by all the preceding evangelists. This is one of the circumstances, which the others may have neglected, to unite three similar facts, and relating to the same object. (Bible de Vence)
St. Peter, the prince and head of the Church, was permitted to fall, to teach him to treat with more mildness and condescension those, whom he would afterwards have to raise out of the same miserable state of sin. One weak and frail man is placed over another, that seeing him unhappily fallen, he may give him his kind and helping hand, to free him from that unhappy state, in which he knows himself to have been. (St. Chrysostom)
Of all which our divine Saviour suffered in the court of Caiphas, nothing so much affected him as the dangerous fall of Peter, the chief of all his apostles, who had received the most signal favours from him. He had boasted that very night, that although all the rest of the disciples should abandon thei...
What do you say, Peter? Did you not declare but now, If need be that I lay down my life for You, I will lay it down? What has happened then, that you can not even endure the questioning of a door-keeper? Is it a soldier who questions you? Is it one of those who seized Him? No, it is a mean and abject door-keeper, nor is the questioning of a rough kind. She says not, Are you a disciple of that cheat and corrupter, but, of that man, which was the expression rather of one pitying and relenting. But Peter could not bear any of these words. The, Are you not also, is said on this account, that John was within. So mildly did the woman speak. But he perceived none of this, nor took it into his mind, neither the first time, nor the second, nor the third, but when the cock crew; nor did this even bring him to his senses, till Jesus gave him the bitter look. And he stood warming himself with the servants of the high priest, but Christ was kept bound within. This we say not as accusing Peter, b...