And it came to pass, as he was alone praying, his disciples were with him: and he asked them, saying, Whom say the people that I am? They answering said, John the Baptist; but some say, Elijah; and others say, that one of the old prophets is risen again. He said unto them, But whom say you that I am? Peter answering said, The Christ of God. And he sternly charged them, and commanded them to tell no man that thing; Saying, The Son of man must suffer many things, and be rejected of the elders and chief priests and scribes, and be slain, and be raised the third day.

And he said to them all, If any man will come after me, let him deny himself, and take up his cross daily, and follow me. For whosoever will save his life shall lose it: but whosoever will lose his life for my sake, the same shall save it. For what is a man profited, if he gain the whole world, and lose himself, or suffer loss? For whosoever shall be ashamed of me and of my words, of him shall the Son of man be ashamed, when he shall come in his own glory, and in his Father's, and of the holy angels. But I tell you a truth, there be some standing here, who shall not taste of death, till they see the kingdom of God.

And it came to pass about eight days after these sayings, he took Peter and John and James, and went up into a mountain to pray. And as he prayed, the appearance of his countenance was altered, and his clothing was white and glistening. And, behold, there talked with him two men, who were Moses and Elijah: Who appeared in glory, and spoke of his death which he should accomplish at Jerusalem. But Peter and they that were with him were heavy with sleep: and when they were awake, they saw his glory, and the two men that stood with him.

And it came to pass, as they departed from him, Peter said unto Jesus, Teacher, it is good for us to be here: and let us make three tabernacles; one for you, and one for Moses, and one for Elijah: not knowing what he said. While he thus spoke, there came a cloud, and overshadowed them: and they feared as they entered into the cloud. And there came a voice out of the cloud, saying, This is my beloved Son: hear him. And when the voice was past, Jesus was found alone. And they kept it close, and told no man in those days any of those things which they had seen.
(Luke 9:18-36)