In our Lord’s time the Jews had adopted the Greek and Roman division of the night into four watches, each consisting of three hours, the first beginning at six o’clock in the evening (Luke 12:38; Matt. 14:25; Mark 6:48). But the ancient division, known as the first and second cock-crowing, was still retained. The cock usually crows several times soon after midnight (this is the first crowing), and again at the dawn of day (and this is the second crowing). Mark mentions (14:30) the two cock-crowings. Matthew (26:34) alludes to that only which was emphatically the cock-crowing, viz, the second.
Cock Crowing
A rooster’s call marks the worst night of Peter’s life. Jesus tells him, “before the cock crow twice, thou shalt deny me thrice”, and then it happens exactly so. In Mark 14:68 Peter says he does not know what is meant, and the cock crows. In Matthew 26:75 he remembers the word of Jesus, goes out and weeps bitterly. Mark 13:35 uses the cockcrowing differently, as one of the night hours when a master of the house might return, so “Watch ye therefore”. Matthew 26:69-75 tells the denial in full, and it is a good passage for reading slowly.
7 verses
Matthew
Jesus said unto him, Verily I say unto thee, That this night, before the cock crow, thou shalt deny me thrice.
Then began he to curse and to swear, saying, I know not the man. And immediately the cock crew.
And Peter remembered the word of Jesus, which said unto him, Before the cock crow, thou shalt deny me thrice. And he went out, and wept bitterly.
Mark
Watch ye therefore: for ye know not when the master of the house cometh, at even, or at midnight, or at the cockcrowing, or in the morning:
And Jesus saith unto him, Verily I say unto thee, That this day, even in this night, before the cock crow twice, thou shalt deny me thrice.
But he denied, saying, I know not, neither understand I what thou sayest. And he went out into the porch; and the cock crew.
And the second time the cock crew. And Peter called to mind the word that Jesus said unto him, Before the cock crow twice, thou shalt deny me thrice. And when he thought thereon, he wept.
From Easton's Bible Dictionary
Matthew George Easton, 1897