Cyril of Alexandria
Catena Aurea · Lukasevangelium 9
And it came to pass, as he was alone praying, his disciples were with him: and he asked them, saying, Whom say the people that I am? They answering said, John the Baptist; but some say, Elias; and others say, that one of the old prophets is risen again. He said unto them, But whom say ye that I am? Peter answering said, The Christ of God. And he straitly charged them, and commanded them to tell no man that thing; Saying, The Son of man must suffer many things, and be rejected of the elders and Chief Priests and Scribes, and be slain, and be raised the third day.
Now His engaging in prayer might perplex His disciples. For they saw Him praying like a man, Whom before they had seen performing miracles with divine power. In order then to banish all perplexity of this kind, He asks them this question, not because He did not know the reports which they had gathered from without, but that He might rid them of the opinion of the many, and instil into them the true faith. Hence it follows, And he asked them, saying, Whom say the people that I am?