SCRIPTURE COMMENTARY #531
But Peter sat without in the court. And there came to him a servant maid, saying: "Thou also wast with Jesus the Galilean." But he denied before them all, saying: "I know not what thou sayest." And as he went out of the gate, another maid saw him; and she saith to them that were there: "This man also was with Jesus of Nazareth." And again he denied with an oath: "I know not the man." And after a little while, they came that stood by and said to Peter: "Surely thou also art one of them. For even thy speech doth discover thee." Then he began to curse and to swear that he knew not the man. And immediately the cock crew. And Peter remembered the word of Jesus which he had said: "Before the cock crow, thou wilt deny me thrice." And going forth, he wept bitterly. (Matt. 26:69-75)
PETER'S FALL SHOULD BE A WARNING TO US, to carefully avoid bad companions, and the occasions of sin; to remember our weakness and instability; and not to trust too much in ourselves, but to ask humbly for the assistance of grace. It was not without reason that our Lord taught us to pray: "Lead us not into temptation!" St. Paul says (I Cor. 10:12): "He that thinketh himself to stand, let him take heed lest he fall!"
[From 'A Practical Commentary on Holy Scripture' by Bishop Knecht, D.D.]
(1899 Douay-Rheims Bible)