Cyril of Alexandria

Thou seest the skilfulness of the question. He did not at once say, "Whom do ye say that I am?" but refers to the rumour of those that were without, that having rejected it, and shewn it to be unsound, He may then bring them back to the true opinion. Which also happened: for when the disciples had said, "Some John the Baptist, and others Elijah, and others, that some prophet of those in old time has risen up;" He said to them, "But ye, whom do ye say that I am?" Oh! …

Commentary On Luke, Homily 49 ↗

Ambrose of Milan

But it is no trifling opinion of the multitude which the disciples mention, when it is added, But they answering said, John the Baptist, (whom they knew to be beheaded;) but some say, Elias, (whom they thought would come,) but others say that one of the old Prophets is risen again. But to make this enquiry belongs to a different kind of wisdom from ours, for if it were enough for the Apostle Paul to know nothing but Christ Jesus, and Him crucified, what more can I desire to know than Christ? (1 Cor. 2:2.)

Catena Aurea by Aquinas ↗

Bonaventure

For this reason there is subjoined a threefold opinion taken from a threefold excellence. As to the first he says: But they answered and said: John the Baptist: and this, because they saw in him the spirit of sanctification, which was in John, according to that passage above in the first chapter: "He shall be great before the Lord and shall be filled with the Holy Spirit," etc. …

Commentary on Luke, Chapter 9 ↗