Matthew 16:16

The Christ] i.e. 'the Messiah.' So also St. Mark; but St. Luke has 'the Christ of God.' The Son of the living God] These words, together with the next three vv., are peculiar to St. Matthew, but are nevertheless authentic. They suit the context admirably, and are so thoroughly Hebraic in spirit, that their significance can only be apprehended by going behind the Greek to the Aramaic original. Their absence from St. Mark is readily explained. In confessing that Jesus was the Christ, Peter did no more than express the general sense of the apostolic circle. But in confessing that He was the 'Son of the living God,' he was going beyond what the others at that time believed. He, therefore, modestly suppressed his own personal confession and the special commendation with which Jesus greeted it.

'Son of God' here is no mere equivalent of 'the Messiah,' but a confession of Christ's unique filial relation to God. This is shown, (1) by the deep emotion with which the speaker makes, and Jesus receives, the confession; (2) by the fact that the confession is perfectly satisfactory to Jesus, and is forthwith made the dogmatic foundation of Christianity('Upon this rock I will build my Church').