Today is the feast of the Transfiguration. Matthew, Mark and Luke all tell the story in their Gospels. The Gospel writers felt great freedom to arrange the particulars of Jesus' teachings and actions to suit the purposes of their own particular Gospel. Here, though, they all follow the same sequence of events. You have Peter's confession, that Jesus is the Christ, the son of the living God, and Jesus' revelation that he will be killed in Jerusalem and be raised on the third day. And after this (and after rebuking Peter), in all three Gospels, he tell the disciples that "there are some standing here who will not taste death before they see the kingdom of God." What comes next is the Transfiguration on the mountain. Moses and Elijah stand with Jesus. Peter, James and John stand looking on, and God's glory comes overshadowing all. The law, in the person of Moses, the prophets, in the person of Elijah, the apostles, present, but bewildered, all witnessing the Reign of God revealed in the Uncreated Light shining forth from Jesus. This image, which hearkens back to Moses on Sinai and looks forward to the radiance of the New Jerusalem, is key to understanding Orthodox spirituality.
Here is a hymn from Ephraim the Syrian on the feast, from Anastasis, the web page of Archimandrite Ephraim of the Monastery of Saint Andrew:
He led them up the mountain to show them the glory of the godhead and to make known to them that he is the redeemer of Israel, as he had shown through the Prophets, and that they should not be scandalised in him when they saw his voluntary sufferings, that as man he was about to suffer for us. For they knew him as a man, but did not know that he was God. They knew him as son of Mary, going about with them in the world, and he made known to them on the mountain that he was Son of God and God.
The troparian and kontakian (special hymns) for the feast follow:
Thou wast transfigured on the mount, O Christ God,/ revealing Thy glory to Thy disciples as far as they could bear it./ Let Thine everlasting light shine upon us sinners/ through the prayers of the Theotokos, O Giver of Light, glory to Thee.
Thou wast transfigured on the mountain, O Christ our God,/ and Thy disciples beheld Thy glory as far as they were capable,/ that when they should see Thee crucified,/ they might know that Thy suffering was voluntary/ and might proclaim to the world/ that Thou art indeed the reflection of the Father.