The disciples were afraid to ask Jesus about his revelation to them that he will be handed over to the authorities. The Second prophecy of Jesus’ passion (in Luke) could not have occurred at a worse time for the disciples. Jesus had just finished the healing of an epileptic demoniac (which the disciples had been unable to deal with) at the amazement of the crowd who were left reeling at the greatness of God. The disciples must have been still figuring out how to handle this mishap on their road to stardom (they had just returned from their various missions which from all indications had went well). At any other time, the disciples might have asked Jesus to elaborate on this talk of him being handed over for persecution. But on this particular day, their morale was too low for them to even raise their heads. This Jesus really knew how to ruin someone’s day.
Jesus did not want the disciples to lose sight of the wider picture (of their mission). He did not want them to allow fleeting moments such as the excitement of the crowd at some good they had done to steer them away from what was important. There were two sides to the mission of Jesus: the joyous moments and the not so joyous moments. While the joyous moments needed to be shared by all (such as just had happened), the not-so-joyous moments would be left for the disciples to shoulder and deal with. As a people who had “removed” themselves from the world, Jesus was opening their eyes to the fact that a time would come when the very people who were glorifying God because of the disciples’ ministry would make an about-turn and throw stones at them while calling for their execution. Jesus’ words were not meant to scare the disciples but to awaken to the reality and in so doing make them ready (cf. John 14:29 - “I tell you these things so that when they do happen, you may not be surprised”).