The Origins of the Feast
The Feast of the Transfiguration is held to have been founded by Saint Gregory the Illuminator, some time in the early third century, AD. It is said that the Feast took the place of an earlier pagan ritual known as "roseflame", as Christ's transfiguration was also similar to a flaming rose. The Feast was relatively slow to be adopted by the majority of churches, though most took up the practice by the 15th century.
The Story of the Transfiguration
According to the Gospels of Luke (9:28-36), Mark (9:1-8), and Matthew (17:1-6), the Transfiguration occurred when Jesus traveled to the top of a mountain to pray with three of the Apostles, Peter, John, and James. Upon reaching the summit, Jesus was transfigured, his entire body being filled with a shining white light, as though his person were filled with clear fire.
Moments later, the prophets Elijah and Moses appeared to either side of Jesus, and began to speak with him of his burden and impending death. Then, a blazing cloud appeared overhead, and a voice spoke from heaven (typically taken to be God), saying that Jesus was his beloved son, in whom he was well pleased. After the event was over, Jesus asked the three Apostles to keep the occurrence a secret until the Son of Man rose from the dead.
Interpretations of the Transfiguration
Generally speaking, the primary significance of the Transfiguration exists in the light which shines from Jesus' body on the mountaintop, which is typically held to be a sign of his internal divinity fully manifesting itself in the material world. It is also the second of time that he is called a beloved son by a heavenly voice, the first being when he is baptized by John. As a result of these events, the Transfiguration is considered the turning point between Jesus' prophetic ministry and priestly (or divine) ministry.
For hundreds of years, the Transfiguration was considered to be a literal occurrence. In recent centuries, however, the event has come to be seen as an allegory by some Christians, with Elijah and Moses representing the Law and the Prophets, respectively, symbolizing the fulfillment of Jesus' words in Mathew 5:17:
"Do not think that I have come to abolish the Law or the Prophets; I have not come to abolish them but to fulfill them." (NIV)
In effect, Jesus, standing between the Law and the Prophet, became the fulfillment of both in the eyes of God, as evidenced by the commendation of the voice from the clouds.
The popular conception is that the mountain on which the Transfiguration occurred is Mount Tabor, a mountain in Israel west of the Sea of Galilee. Mount Hermon is also sometimes raised as a possible sight, but is considered an unlikely option because it would have been snow-covered and hard to travel at the time of the Transfiguration, and the Gospels make no mention of snow.
For Christians around the world, the Transfiguration remains an important observance. It is a chance to reflect upon the glorious divinity of Christ made manifest in the material world.