Peter again denied it, and at once a rooster crowed.
27. 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...
We have here an account of Christ's arraignment before the high priest, and some circumstances that occurred therein which were omitted by the other evangelists; and Peter's denying him, which the other evangelists had given the story of entire by itself, is interwoven with the other passages.
Commenting on John 18:13-27
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.