Transfiguration of our Lord
According to the evangelist Matthew, Jesus took the apostles Peter, James, and John to a mountain, where he was illuminated by a bright heavenly light. The Jewish patriarch Moses and the prophet Elijah then appeared and a voice from a cloud declared Jesus to be the son of God.
The feast of the Transfiguration is one of the major holidays of the Ukrainian Greek Catholic church, occuring on August 6th in the Gregorian Calendar.
The depicted icon is similar to many early Byzantine Icons.
St. Matthew 17:1-6
And after six days Jesus took with him Peter and Jams and John his brother, and led them up a high mountain apart. And he was trasfigured before them, and his face shone like the sun, and his garments became white as light. And behold there appeared to them Moses and Elijah, 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 Elijah. "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 Jesuis came and touched them, saying, "Rise, and have no fear." And when they lifted up their eyes, they saw no one but Jesus only.
St. Mark 9:1-13
And after six days Jesus took with him Peter and James, and John, and led them up a high mountain apart by themseleves; and he was transfigured before them, and his garments became glistening, inten sely white, as no fuller on earth could bleach them. And there appeared to them Elijah with Moses; and they were talking to Jesus. And Peter waid to Jesus, "Master, it is well that we are here; let us make three boths, one for you and one for Moses and one for Elijah.." For he did not know what to say, for they were exceedingly afraid. And a cloud overshadowed them, and a voice came out of the cloud, "This is my beloved Son; listen to him." And suddenly looking around they no longer saw any one with them but Jesus only. And as they were comming down the mountain, he charged them to tell no one whay they had seen, until the sone of man should have risen from the dead. So they kept the matter to themseleves, questioning what the rising from the dead meant. And they asked him, "Why do the scribes say that first Elijah must come?" And he said to them, "Elijah does come first to restore all things; and how ist it written of the Son of man, that hey should suffer many things and be treated with contempt? But I tell you that Elijah has come, and they did to him whatever they pleased, as it is written of him."
St. Luke 9:28-36
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 praining, the appearance of his countenance was altered, and his raiment became dazzling white. And behold, two men talked wioth him, Moses and Elijah, who appeared in glory and spoke of his departure, which he was to accomplish at Jerusalem. Now Peter and those who were with him were heavy with sleep but kept awake, and 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 well that we are here; let us make three booths, one for you and one for Moses and one for Elijah" - not knowing that he said. As he said this, a cloud cam e and over shadowed 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, listen to him!" And when the voice had spoken, Jesus was found alone. And they kept silence and told no one in those days anything of what they had seen.
See also
http://www.newadvent.org/cathen/15019a.htm