A.T. Robertson Commentary Mark 8:29

"And he asked them, But who say ye that I am? Peter answereth and saith unto him, Thou art the Christ." — Mark 8:29 (ASV)

Thou art the Christ (Συ ε ο Χριστος). Mark does not give "the Son of the living God" (Matthew 16:16) or "of God" (Luke 9:20). The full confession is the form in Matthew. Luke's language means practically the same, while Mark's is the briefest. But the form in Mark really means the full idea. Mark omits all praise of Peter, probably because Peter had done so in his story of the incident. For criticism of the view that Matthew's narrative is due to ecclesiastical development and effort to justify ecclesiastical prerogatives, see discussion on Mt 16:16,18. The disciples had confessed him as Messiah before. Thus Joh 1:41; 4:29; 6:69; Matthew 14:33. But Jesus had ceased to use the word Messiah to avoid political complications and a revolutionary movement (John 6:14f.). But did the disciples still believe in Jesus as Messiah after all the defections and oppositions seen by them? It was a serious test to which Jesus now put them.