Now about eight days after these sayings he took with him Peter and John and James and went up on the mountain to pray.  And as he was praying, the appearance of his face was altered, and his clothing became dazzling white.  And behold, two men were talking with him, Moses and Elijah,  who appeared in glory and spoke of his departure, which he was about to accomplish at Jerusalem.  Now Peter and those who were with him were heavy with sleep, but when they became fully awake they saw his glory and the two men who stood with him.  And as the men were parting from him, Peter said to Jesus, “Master, it is good that we are here. Let us make three tents, one for you and one for Moses and one for Elijah”—not knowing what he said.  As he was saying these things, a cloud came and overshadowed them, and they were afraid as they entered the cloud.  And a voice came out of the cloud, saying, “This is my Son, my Chosen One; listen to him!”  And when the voice had spoken, Jesus was found alone. And they kept silent and told no one in those days anything of what they had seen.
 On the next day, when they had come down from the mountain, a great crowd met him.  And behold, a man from the crowd cried out, “Teacher, I beg you to look at my son, for he is my only child.  And behold, a spirit seizes him, and he suddenly cries out. It convulses him so that he foams at the mouth, and shatters him, and will hardly leave him.  And I begged your disciples to cast it out, but they could not.”  Jesus answered, “O faithless and twisted generation, how long am I to be with you and bear with you? Bring your son here.”  While he was coming, the demon threw him to the ground and convulsed him. But Jesus rebuked the unclean spirit and healed the boy, and gave him back to his father.  And all were astonished at the majesty of God.
But while they were all marveling at everything he was doing, Jesus said to his disciples,  “Let these words sink into your ears: The Son of Man is about to be delivered into the hands of men.”  But they did not understand this saying, and it was concealed from them, so that they might not perceive it. And they were afraid to ask him about this saying.
(Luke 9:28-45 ESV)