See the Matthew 16:13-27 notes; Mark 8:27-38 notes.

Whom say the people - Οἱ οχλοι, the common people, i.e. the mass of the people. See this question considered on Matthew 16:13 (note), etc.

And it came to pass, as he was alone praying,.... To his God and Father, for himself as man, and mediator; for the success of his Gospel, and the increase of his interest; and for his disciples, that they might have a clearer revelation of him; and which they had, as appears in their after confession of him by Peter, as the mouth of them all. The place where he now retired for private devotion, was somewhere in the coasts of Caesarea Philippi; for he was now gone from the desert of Bethsaida, as appears from Matthew 16:13 and when he is said to be alone, the meaning is, that he was retired from the multitude, but not from his disciples; for it follows,

his disciples were with him, in this solitary place:

and he asked them, being with them alone;

saying, Whom say the people that I am? what are the sentiments of the common people, or of the people in general concerning me? The Alexandrian copy, and the Arabic version read, "men", as in Matthew 16:13. See Gill on Matthew 16:13.

As he was praying

Peculiar to Luke.

{4} And it came to pass, as he was {f} alone praying, his disciples were with him: and he asked them, saying, Whom say the people that I am?

(4) Although the world be tossed up and down between different errors, yet we ought not to condemn the truth but be all the more desirous to know it, and be more steadfast to confess it.

(f) Alone from the people.

9:18-21 He was alone praying. Only Luke informs us of this, his disciples being present, when he asked the question,

Whom say the people that I am? See notes on Peter's confession of faith, Mt 16:13-20 Mr 8:27-30.

9:18 Apart - From the multitude. And he asked them - When he had done praying, during which they probably stayed at a distance. Mt 14:13; Mr 8:27.

Lu 9:18-27. Peter's Confession of Christ-Our Lord's First Explicit Announcement of His Approaching Death, and Warnings Arising Out of It.

(See on [1609]Mt 16:13-28; and Mr 8:34).

9:18-27 It is an unspeakable comfort that our Lord Jesus is God's Anointed; this signifies that he was both appointed to be the Messiah, and qualified for it. Jesus discourses concerning his own sufferings and death. And so far must his disciples be from thinking how to prevent his sufferings, that they must prepare for their own. We often meet with crosses in the way of duty; and though we must not pull them upon our own heads, yet, when they are laid for us, we must take them up, and carry them after Christ. It is well or ill with us, according as it is well or ill with our souls. The body cannot be happy, if the soul be miserable in the other world; but the soul may be happy, though the body is greatly afflicted and oppressed in this world. We must never be ashamed of Christ and his gospel.