This night - This was in the "evening" when this was spoken, after the observance of the Passover, and, we may suppose, near nine o'clock p.m.
Before the cock crow - Mark and Luke add, before the cock crowed twice. The cock is accustomed to crow twice once at midnight, and once in the morning at break of day. The latter was commonly called cock-crowing. See Mark 13:35. This was the time familiarly known as "the cock-crowing," and of this Matthew and John speak, without referring to the other. Mark and Luke speak of the "second" crowing, and mean the same time, so that there is no contradiction between them.
Deny me thrice - That is, as Luke adds, deny that "thou knowest" me. See Matthew 26:74.

Jesus said - Our Lord's answer to Peter is very emphatic and impressive. Verily - I speak a solemn weighty truth, thou wilt not only be stumbled, fall off, and forsake thy Master, but thou wilt even deny that thou hast, or ever had, any knowledge of or connection with me; and this thou wilt do, not by little and little, through a long process of time, till the apostasy, daily gathering strength, shall be complete; but thou wilt do it this very night, and that not once only, but thrice; and this thou wilt do also in the earlier part of the night, before even a cock shall crow. Was not this warning enough to him not to trust in his own strength, but to depend on God?

Jesus said unto him, verily I say unto thee,.... Christ, the more strongly to asseverate what he was about to say, uses the word verily, or prefixes his "Amen" to it, as being a certain truth, and what Peter might assure himself of would certainly come to pass:
that this night before the cock crow, thou shalt deny me thrice; which is, as if he should say, thou wilt not only be offended because of me, and flee from me, and be scattered with the rest, as will be the case of all of you; but thou wilt deny that thou knowest me, that thou belongest to me, or hast any concern with me; and this thou wilt do not only once, but again and again, even three times, one after another, and that this very night, before the cock has done crowing. In Mark it is said, "that this day, even in this night, before the cock crow twice, thou shalt deny me thrice",
Mark 14:30; which may be reconciled with the words of Matthew, and the other evangelists, by observing, that the word "twice" is not in Beza's ancient copy, which he gave to the university of Cambridge, nor is it in the Ethiopic version; which if allowed to be the true reading, the difficulty is removed at once; but whereas it is in other copies, no stress must be laid on this, nor is there any need of it: for whereas the cock crows twice in the night, once at midnight, and again near break of day; and which latter crowing being louder, and more welcome, and most taken notice of, is, by way of eminence, called the cock crowing; and is what Matthew here has respect to, and so designs the same as Mark does; and the sense of both is, that before the cock crow a second time, which is most properly the cock crowing, Peter should three times deny his master, as he did; see Mark 13:35, where cock crowing is distinguished from midnight, the first time the cock crows, and means the second time of crowing; and where Mark is to be understood in the same sense as Matthew, and both entirely agree. So cock crowing and midnight are distinguished by the Jews, who say (b),
"that on all other days they remove the ashes from the altar, , "at cock crowing", or near unto it, whether before or after; but on the day of atonement,
"at midnight":
and who also speak of the cocks crowing a first and second, and even a third time (c),
"Says R. Shila, he that begins his journey before cock crowing, his blood be upon his head. R. Josiah says, he may not proceed , "until he repeats"; that is, until he crows twice: and there are, who say, until he trebles it, or crows a third time: of what do they speak? of a middling one, i.e. which neither crows too soon, nor too late.
(b) Misn. Yoma, c. 1. sect. 8. (c) T. Bab. Yoma, fol. 21. 1.

Thou shalt deny me thrice. The first cock crow was about twelve at night. The second about three o'clock. Before this the three-fold denial would occur. Peter and the disciples were sincere, but knew not their own weakness.

Before cock crowing thou wilt deny me thrice - That is, before three in the morning, the usual time of cock crowing: although one cock was heard to crow once, after Peter's first denial of his Lord.