He had just finished feeding the 5,000 men plus women and children when he asked them the question (Luke 9:10-17). In this context of feeding people (cf. Luke 24:28-35) Jesus asked his disciples, "Who do the crowds say that I am?" (Luke 9:18). We stand here at a turning point in Luke's story of Jesus. In earlier stories of Jesus' baptism, genealogy, temptation and a sabbath in his hometown synagogue Luke has given us all kinds of clues as to the identity of Jesus. After that there comes action. Jesus healed people. He forgave sinners. He called disciples. He challenged sabbath laws and so on. It's time now to return to the question of identity. Do even the disciples understand who this man is? Does anyone really understand?
The disciples answered Jesus question by stating the opinions of some in the crowds. Jesus' then zeroes in on the disciples themselves. "But who do you say that I am?" (Luke 9:20). "The Messiah of God," Peter answered.
And then Jesus did a surprising thing. He acknowledged that Peter had the right answer to his question. But he told the disciples not to tell anyone the truth of his identity. The coming of the Messiah would move Israel from one degree of glory to another. But Jesus was not to be this Messiah of glory. Jesus was to be a Messiah on a cross. Jesus tells it straight in a new revelation of his identity. "The Son of Man must undergo great suffering, and be rejected by the elders, chief priests, and scribes, and be killed and on the third day be raised" (Luke 9:22).
The disciples must have been stunned. They had glory on their minds, too. But, no, the way of this Messiah was to be a way of suffering for him and for the disciples. "If any want to become my followers, let them deny themselves and take up their cross daily and follow me" (Luke 9:23). The disciples never could get this through their heads. In the story of the transfiguration which Luke tells next we hear Jesus discussing the departure he would accomplish in Jerusalem. Jesus, that is, was discussing with Moses and Elijah his way to Jerusalem, his way to the cross. And the disciples? They wanted to build booths and live on this mountain of glory and transfiguration forever. They did not know what they were saying, Luke tells us.
This hardness of heart of the disciples appears again when they all come down from the Mount of Transfiguration. A man comes to Jesus in order that Jesus might heal his son who is possessed by a demon. "I begged your disciples to cast it out, but they could not," the father says to Jesus. Jesus proceeds to wonder aloud about the faithless disciples. He tells them again, therefore, of his mission. "Let these words sink into your ears," he tells them, "The Son of Man is going to be betrayed into human hands." Sadly Luke tells us of the disciples that, "... they did not understand this saying; its meaning was concealed from them, so they could not perceive it" (Luke 9:44-45). The disciples prove the truth of this statement by turning to a discussion among themselves about which one of them was the greatest. They're still thinking of glory!
Jesus has revealed that he must go to Jerusalem to suffer, to die and to be raised again. The disciples don't get it at all. With his heart heavy with the suffering that lay ahead, therefore, and with his mind puzzled by disciples who failed to understand, Jesus set his face to go to Jerusalem.