Mark 8:29

And he saith unto them, but whom say ye that I am?
&c.] It was for the sake of this question he put the former; (See Gill on Matthew 16:15);

and Peter answereth and saith unto him, thou art the Christ;
the Messiah that was long ago promised and so often prophesied of in the books of Moses and the prophets; and whom the Jews have so much and long expected. This confession of Peter's in which all the apostles agreed with him speaks out what Jesus really was, and exceeds the most exalted sentiments which the people had of him: he was not the harbinger of the Messiah but the Messiah himself; not Elias in whose Spirit his forerunner was to come and did come; nor any one of the prophets; but he who was spoken of by all the holy prophets; which have been since the beginning of the world. Not one of the various opinions of the people being just, and answering the true character of Jesus, he demands the sense of his disciples which is here given by Peter in their name, and which was right; and on account of which he declared Peter blessed and ascribed his knowledge of him not to flesh and blood but to the revelation of his Father. The Syriac and Persic versions add, "the Son of the living God"; and so Beza found it in one ancient copy; but it may be it is only taken from Mt 16:16; (See Gill on Matthew 16:16).