Now when Jesus came into the district of Caesarea Philippi, he asked his disciples, “Who do people say that the Son of Man is?” And they said, “Some say John the Baptist, others say Elijah, and others Jeremiah or one of the prophets.” He said to them, “But who do you say that I am?” Simon Peter replied, “You are the Christ, the Son of the living God.” And Jesus answered him, “Blessed are you, Simon Bar-Jonah! For flesh and blood has not revealed this to you, but my Father who is in heaven.
This account also appears in Mark 8:27-30 and Luke 9:18-21.
Caesarea Philippi - a town in the northwest corner of Galilee, near the source of the Jordan River
"This Caesarea was in Herod Philip's territory, about 25 mi (40 km) N of the Sea of Galilee." (Ryrie)
It was clear to everyone that Jesus was someone out of the ordinary, someone who had to be explained supernaturally.
John the Baptist - Herod thought this was who Christ was (Matthew 14:2)
Elijah - his coming is prophesied in Malachi 4:5
Jeremiah - he is sometimes thought to be the prophet in Deuteronomy 18:15. Some thought Jeremiah 11:19 pointed at that prophet as the fulfillment of Isaiah 53:7.
"Some must have seen resemblances between Christ's teachings and those of these great prophets." (Ryrie)
"Peter was a Hebrew, a child of the Hebrew race. He was born in its midst, and had been nurtured upon its thinking. Every fiber of his personality was affected by its conceptions, and it was as a Hebrew that he said to the Man who styled Himself “the Son of Man,” “Thou are the Christ,” the Messiah. That is, Thou are the fulfiller of all the expectations of the Hebrew people, the One by whom our hopes are to be realized, the One by in whom the economy culminates, the One from whom there is to break the dawn of a new day and a new era … Peter’s confession was a very definite one, and yet one that recognized his consciousness of the mystic element in this Man, beyond the things the age had seen. The age had caught the comprehensiveness of the prophetic note. The age had recognized more — the supernaturalness of this Teacher. Peter, recognizing all this, defined it, and went beyond the age, and said; “Thou are the Messiah;” more than John the forerunner, more than Elijah the foreteller, more than Jeremiah the watcher and the one who waited; Thou art the One toward whom they all looked. There is manifested in all Thy doing, and in all Thy teaching something that differentiates Thee from all other teachers and men. Son of Man, but Son of the living God, the Messiah." ( Morgan)
Blessed are you - "...because he had received this insight through divine revelation and not through human influences." (Ryrie)