John Chrysostom

From the manner, however, itself of the question, He leads them to a higher feeling, and to higher thoughts, concerning Him, that they might not agree with the multitude. But the next words show what the head of the disciples, the mouth of the Apostles, answered; when all were asked, Peter answereth and saith unto him, Thou art the Christ.

Catena Aurea by Aquinas ↗

Theophylact of Ohrid

After however having enquired into the opinion of others, He asks them what was the belief of their own minds on this point; wherefore it continues, And he saith unto them, But whom say ye that I am? He confesses indeed that He is the Christ announced by the Prophets; but the Evangelist Mark passes over what the Lord answered to his confession, and how He blessed him, lest by this way of relating it, he should seem to be favouring his master Peter; Matthew plainly goes through the whole of it.

Catena Aurea by Aquinas ↗

Bede

Peter answered, saying: You are the Christ. Although the other apostles knew, Peter responded before the others. He encompassed everything, expressing both nature and name, in which is the summit of virtues. Do we indeed discuss questions about the generation of God? When Paul indicated knowing nothing except Christ Jesus, and him crucified, and Peter thought nothing more than that Christ should be confessed as the Son of God, do we examine with human frailty when and how he was born, and how great he is? …

On the Gospel of Mark ↗