And after six days Jesus took with him Peter and James and John his brother, and led them up a high mountain apart. And he was transfigured before them, and his face shone like the sun, and his garments became white as light. And behold, there appeared to them Moses and Eli'jah, talking with him. And Peter said to Jesus, "Lord, it is well that we are here; if you wish, I will make three booths here, one for you and one for Moses and one for Eli'jah." He was still speaking, when lo, a bright cloud overshadowed them, and a voice from the cloud said, "This is my beloved Son, with whom I am well pleased; listen to him." When the disciples heard this, they fell on their faces, and were filled with awe. But Jesus came and touched them, saying, "Rise, and have no fear." And when they lifted up their eyes, they saw no one but Jesus only. And as they were coming down the mountain, Jesus commanded them, "Tell no one the vision, until the Son of man is raised from the dead." (Matthew 17:1-9, RSV)
"After these words I glanced at his face and there came over me an even greater reverent awe. Imagine in the center of the sun, in the dazzling light of its midday rays, the face of a man talking to you. You see the movement of his lips and the changing expression of his eyes, you hear his voice, you feel someone holding your shoulders; yet you do not see his hands, you do not even see yourself or his figure, but only a blinding light spreading far around for several yards and illumining with its glaring sheen both the snow-blanket which covered the forest glade and the snow-flakes which besprinkled me and the great Elder. You can imagine the state I was in!"
(From "St. Seraphim of Sarov's Conversation With Nicholas Motovilov: A Wonderful Revelation to the World")