P1748:1, 157:5.1 The new and vital feature of Peter's confession was the clear-cut recognition that Jesus was the Son of God, of his unquestioned divinity. Ever since his baptism and the wedding at Cana these apostles had variously regarded him as the Messiah, but it was not a part of the Jewish concept of the national deliverer that he should be divine. The Jews had not taught that the Messiah would spring from divinity; he was to be the "anointed one," but hardly had they contemplated him as being "the Son of God." In the second confession more emphasis was placed upon the combined nature, the supernal fact that he was the Son of Man and the Son of God, and it was upon this great truth of the union of the human nature with the divine nature that Jesus declared he would build the kingdom of heaven.
P1748:2, 157:5.2 Jesus had sought to live his life on earth and complete his bestowal mission as the Son of Man. His followers were disposed to regard him as the expected Messiah. Knowing that he could never fulfill their Messianic expectations, he endeavored to effect such a modification of their concept of the Messiah as would enable him partially to meet their expectations. But he now recognized that such a plan could hardly be carried through successfully. He therefore elected boldly to disclose the third plan -- openly to announce his divinity, acknowledge the truthfulness of Peter's confession, and directly proclaim to the twelve that he was a Son of God.
P1748:3, 157:5.3 For three years Jesus had been proclaiming that he was the "Son of Man," while for these same three years the apostles had been increasingly insistent that he was the expected Jewish Messiah. He now disclosed that he was the Son of God, and upon the concept of the combined nature of the Son of Man and the Son of God, he determined to build the kingdom of heaven. He had decided to refrain from further efforts to convince them that he was not the Messiah. He now proposed boldly to reveal to them what he is, and then to ignore their determination to persist in regarding him as the Messiah.