Luke 9:20

In this one name there is the expression both of His divinity and incarnation, and the belief of His passion. He has therefore comprehended every thing, having expressed both the nature and the name wherein is all virtue. (summa virtutum)

But mark the subtle skill of the question. For he directs them first to the praises of strangers, that having overthrown these, He might beget in them the right opinion. So when the disciples had given the opinion of the people, He asks them their own opinion; as it is added, And He said unto them, Whom say ye that I am? How marked is ye! He excludes them from the other, that they may avoid their opinions; as if He said, Ye who by my decree are called to the Apostleship, the witnesses of my miracles, whom do ye say that I am? But Peter anticipated the rest, and becomes the mouthpiece of the whole company, and launching forth into the eloquence of divine love, utters the confession of faith, as it is added, Peter answering said, The Christ of God. He says not merely that He was Christ of God, but now He uses the article. Hence it is in the Greek, τὸν χριστόν. For many divinely accounted persons are in diverse ways called Christs, for some were anointed kings, some prophets. But we through Christ have been anointed by the holy Spirit, have obtained the name of Christ. But there is only one who is the Christ of God and the Father, He alone as it were having His own Father who is in heaven. And so Luke agrees indeed in the same opinion as Matthew, who relates Peter to have said, Thou art Christ, the Son of the living God, but speaking briefly Luke says that Peter answered, the Christ of God. But we must observe, that Peter most wisely confessed Christ to be one, against those who presumed to divide Immanuel into two Christs. For Christ did not enquire of them, saying, Whom do men say the divine Word is? but the Son of man, whom Peter confessed to be the Son of God. Herein then is Peter to be admired, and thought worthy of such chief honour, seeing that Him whom he marvelled at in our form, he believed to be the Christ of the Father, that is to say, that the Word which proceeded of the Father's Substance was become man.