John Chrysostom — as excerpted in the Catena Aurea on Mark 8:27-33

“But how is this, that Peter, gifted with a revelation from the Father, has so soon fallen, and become unstable? Surely, however, it was not wonderful that one who had received no revelation concerning the Passion should be ignorant of this. For that He was the Christ, the Son of the living God, he had learnt by revelation; but the mystery of His cross and resurrection had not yet been revealed to him. He Himself, however, shewing that He must come to His Passion, rebuked Peter; wherefore there follows, And when he had turned about and looked on his disciples, he rebuked Peter, &c.”