revelation

And Simon Peter answered and said, Thou art the Christ, the Son of the living God (Matt. 16:16).

This was the first teaching revealed to the Church: Jesus is the Christ, the Son of the living God. It is therefore at all times the first teaching of the Church and, with respect to mankind, the most important. And it was indeed revealed, for Jesus answered him saying, "Blessed art thou, Simon son of John: for flesh and blood hath not revealed it unto thee, but my Father which is in heaven" (16:17). Peter was blessed with the knowledge of who Christ is, which was given to him by the Father and therefore was infallible: for God does not lie.