John Chrysostom

O what strange and remarkable turns occur in these ironic events! When Peter merely saw his master seized, he was so ardent as both to draw his sword and to whack off the servant's ear! But—alas, then when it might have been even more plausible for him to be even more indignant, and to be inflamed and to burn, upon hearing such revilings against his Lord, then he became a cringing denier … and that in the presence of a lowly and diminutive maidservant, and not only once but a second and third time.

The Gospel Of St Matthew, Homily 85.1 ↗

Theophylact of Ohrid

Although Peter was the most fervent of all, nevertheless he proved weak and denied the Lord, having been troubled by fear. And such fear was brought upon him by a mere servant girl! God permitted him to suffer this by a special providence, so that he would not become proud, so that he would be compassionate toward others who fall, having learned from his own experience the depth of human weakness.

Commentary on Mark ↗

Augustine of Hippo

Concerning the temptation of Peter, which happened during the injuries before mentioned, all the Evangelists do not speak in the same order. For Luke first relates the temptation of Peter, then these injuries of the Lord; but John begins to speak of the temptation of Peter, and then puts in some things concerning our Lord's ill-treatment, and adds, that He was sent from there to Caiaphas the High Priest, and then he goes back to unfold the temptation of Peter, which he had begun. …

Catena Aurea by Aquinas ↗

Bede

And while Peter was in the courtyard below, one of the maidservants of the high priest came. And when she saw Peter warming himself, looking at him she said: You also were with Jesus of Nazareth, etc. What does it mean that the maidservant first betrayed him, when surely men could have recognized him more? unless it is that this sex might also appear to have sinned in the death of the Lord and that this sex might also be redeemed through the passion of the Lord. …

On the Gospel of Mark ↗