Given the hardness of the hearts of the disciples (Mark 6:52; Mark 8:17), the only way they could come to understand who Jesus really is, is if Jesus opened their eyes. Jesus had to work in them in order to bring them to this understanding. Just like the blind man needed Jesus to open his eyes so he could see again (Mark 8:22–26), the disciples needed Jesus to open their spiritual eyes so they could understand who he is.
29 And he asked them, “But who do you say that I am?” Peter answered him, “You are the Christ.”