Origen

It must be enquired in this place whether, when they were first sent out, the disciples knew that He was the Christ. For this speech shews that Peter then first confessed Him to be the Son of the living God. And look whether you can solve a question of this sort, by saying that to believe Jesus to be the Christ is less than to know Him; and so suppose that when they were sent to preach they believed that Jesus was the Christ, and afterwards as they made progress they knew Him to be so. Or must we answer thus; That then the Apostles had the beginnings of a knowledge of Christ, and knew some little concerning Him; and that they made progress afterwards in the knowledge of Him, so that they were able to receive the knowledge of Christ revealed by the Father, as Peter, who is here blessed, not only for that he says, Thou art the Christ, but much more for that he adds, the Son of the living God.