Immediately the coch crew. The Evangelist mentions the crowing of the coch, in order to inform us, that Peter was warned by God at the very time; and for this reason the other Evangelists tell us, that he then remembered the words of the Lord, (Matthew 26:75; Mark 14:72,) though Luke relates that the mere crowing of the cock did not produce any effect on Peter, till Christ looked at him, (Luke 22:61.) Thus, when any person has once begun to fall through the suggestions of Satan, no voice, no sign, no warning, will bring him back, until the Lord himself cast his eyes upon him.

And - the cock crew - Peter denied our Lord three times: -
Peter's First Denial.
I. This took place, when he was without, or beneath, in the hall of Caiaphas's house. He was not in the higher part where Christ stood before the high priest; but without that division of the hall, and in the lower part with the servants and officers, at the fire kindled in the midst of the hall, John 18:16, John 18:18; and the girl who kept the door had entered into the hall, where she charged Peter.
Peter's Second Denial.
II. This was in a short time after the first, Luke 22:58. Having once denied his Master, he naturally retired from the place where his accuser was to the vestibule of the hall, Matthew 26:71, and it was the time of the first cock-crowing, or soon after midnight. After remaining here a short time, perhaps an hour, another girl sees him, and says to them who were standing by in the vestibule, that he was one of them. Peter, to avoid this charge, withdraws into the hall, and warms himself. The girl, and those to whom she had spoken, follow him; the communication between the two places being immediate. Here a man enforces the charge of the girl, according to Luke; and others urge it, according to St. John; and Peter denies Jesus vehemently.
Peter's Third Denial.
III. He was now in the hall, and also within sight of Jesus, though at such a distance from him that Jesus could not know what passed, but in a supernatural way. And, about an hour after his second denial, those who stood by founded a third charge against him, on his being a Galilean, which St. Luke says, Luke 22:59, one in particular strongly affirmed; and which, according to John, John 18:26, was supported by one of Malchus's relations. This occasioned a more vehement denial than before, and immediately the cock crew the second time, which is eminently called αλεκτοροφωνια. The first denial may have been between our twelve and one; and the second between our two and three.
At the time of the third denial, Luke 22:61 proves that Jesus was in the same room with Peter. We must farther observe that Matthew, Matthew 26:57, lays the scene of Peter's denials in the house of Caiaphas: whereas John, John 18:15-23, seems to intimate that these transactions took place in the house of Annas; but this difficulty arises from the injudicious insertion of the particle ουν, therefore, in John 18:24, which should be omitted, on the authority of ADES, Mt. BH, many others; besides some versions, and some of the primitive fathers. Griesbach has left it out of the text. See Bishop Newcome's Harm. notes, p. 48.
The time of Peter's denials happened during the space of the third Roman watch, or that division of the night, between twelve and three, which is called αλεκτοροφωνια, or cock-crowing, Mark 13:35. Concerning the nature and progress of Peter's denial, see the notes on Matthew 26:58, Matthew 26:69-75.

Peter then denied again,.... A third time, as the Ethiopic version renders it; and that, according to other evangelists, with cursing and swearing; for now he was more affrighted than before, lest should he be taken up, and it be proved upon him, that he was the person that cut off Malchus's ear, he should be sentenced to a fine, or it may be some capital punishment. The fine for plucking a man's ears, and which some understand of plucking them off, was four hundred "zuzim" (s), or, pence; which, as they answer to Roman pence, amount to twelve pounds ten shillings; a sum of money Peter perhaps could not have raised, without great difficulty: and therefore, that it might be believed he was not a disciple of Christ, so not the man; he swears in a profane manner, and imprecates the judgments of God upon him:
and immediately the cock crew; the second time; which was a signal by which he might call to remembrance, what Christ had said to him; that before the cock crowed twice, he should deny him thrice, Mark 14:72. It was now early in the morning, about three o'clock, or somewhat after.
(s) Misn. Bava Kama, c. 8, sect. 6. Vid. L'Empereur in ib.

Peter then denied again--But, if the challenge of Malchus' kinsman was made simultaneously with this on account of his Galilean dialect, it was no simple denial; for Matthew 26:74 says, "Then began he to curse and to swear, saying, I know not the man." So Mark 14:71. This was THE THIRD DENIAL.
and immediately--"while he yet spake" (Luke 22:60).
the cock crew--As Mark is the only Evangelist who tells us that our Lord predicted that the cock should crow twice (Mark 14:30), so he only mentions that it did crow twice (Mark 14:72). The other Evangelists, who tell us merely that our Lord predicted that "before the cock should crow he would deny Him thrice" (Matthew 26:34; Luke 22:34; John 13:38), mention only one actual crowing, which was Mark's last. This is something affecting in this Evangelist--who, according to the earliest tradition (confirmed by internal evidence), derived his materials so largely from Peter as to have been styled his "interpreter," being the only one who gives both the sad prediction and its still sadder fulfilment in full. It seems to show that Peter himself not only retained through all his after-life the most vivid recollection of the circumstances of his fall, but that he was willing that others should know them too. The immediately subsequent acts are given in full only in Luke (Luke 22:61-62): "And the Lord turned and looked upon Peter," from the hall of judgment to the court, in the way already explained. But who can tell what lightning flashes of wounded love and piercing reproach shot from that "look" through the eye of Peter into his heart! "And Peter remembered the word of the Lord, how He had said unto him, Before the cock crow, thou shalt deny Me thrice. And Peter went out and wept bitterly." How different from the sequel of Judas' act! Doubtless the hearts of the two men towards the Saviour were perfectly different from the first; and the treason of Judas was but the consummation of the wretched man's resistance of the blaze of light in the midst of which he had lived for three years, while Peter's denial was but a momentary obscuration of the heavenly light and love to his Master which ruled his life. But the immediate cause of the revulsion, which made Peter "weep bitterly," was, beyond all doubt, this heart-piercing "look" which his Lord gave him. And remembering the Saviour's own words at the table, "Simon, Simon, Satan hath desired to have you that he may sift you as wheat, but I have prayed [rather, 'I prayed'] for thee that thy faith fail not" (see on Luke 22:31-32), may we not say that this prayer fetched down all that there was in that 'look' to pierce and break the heart of. Peter, to keep it from despair, to work in it "repentance unto salvation not to be repented of," and at length, under other healing touches, to "restore his soul?" (See on Mark 16:7).