This was an event during the earthly life of the Christ which marks the culminating point in his public ministry, and stands midway between the temptation in the wilderness and the agony in Gethsemane, (Matthew 17:1-13; Mark 9:2-13; Luke 9:28-36)
Though tradition locates the transfiguration on Mount Tabor there in fact is little to confirm this view, and modern critics favor Mount Hermon, the highest mountain-top in Gaulanitis, or one of the spurs of the Anti-Lebanus.
The transfiguration may have taken place in the evening or at night, because it could then been seen better than in daylight, and also because Jesus usually went to mountains to spend the night there in prayer. (Matthew 14:23-24; Luke 6:12; 21:37). But this is only a guess.
The apostles were asleep, but are described as getting awake during the transfiguration. (Luke 9:32)
The Christ was the central figure, the subject of the transfiguration. Moses and Elijah to Him, as the representatives of the Old Testament, the one of the law the other of prophecy, to do homage to him who was the fulfillment of both.
Mr. Ellicott says, “The close of the ministry of each was not after the ‘common death of all men.’ No man knew of the sepulchre of Moses, and Elijah had passed away in the chariot and horses of fire. (2 Kings 2:11)
Both were associated in men’s minds with the glory of the Kingdom of the Christ.
The Jerusalem Targum on (Exodus 12:1) connects the coming of Moses with that of the Messiah.
Another Jewish tradition predicts his appearance with that of Elijah.
Moses the law giver and Elijah the chief of the prophets both appear talking with Christ the source of the gospel, to show that they agree in one.
Luke, (Luke 9:31) adds the subject of their communing: “They spake of his decease which he should accomplish at Jerusalem.”
The three favorite disciples, Peter, James and John were the sole witnesses of the scene– “the sons of thunder and the man of rock.”
The transfiguration or transformation, or, as the Germans call it, the glorification, consisted in a visible manifestation of the inner glory of Christ’s person, accompanied by an audible voice from heaven.
It was the revelation and anticipation of his future state of glory, which was concealed under the veil of his humanity in the state of humiliation.
The cloud which overshadowed the witnesses was bright or light-like, luminous, of the same kind as the cloud at the ascension.
The miracle served as a solemn inauguration of the history of the passion and final consummation of Christ’s work on earth.
It confirmed the faith of the three favorite disciples, and prepared them for the great trial which was approaching, by showing them the real glory and power of Jesus.
It was a witness that the spirits of the lawgiver and the prophet accepted the sufferings and the death which had shaken the faith of the disciples as the necessary conditions of the messianic kingdom.
A voice from the eternal Majesty, audibly affirmed that it was the will the Father that with His own precious blood He should make atonement for sin.
They impressed a new seal upon the ancient, eternal truth that the partition wall which sin had raised could he broken down by no other means than by the power of his sufferings; that he as the good Shepherd could only ransom his sheep with the price of his own life.
It furnishes also to us all a striking proof of the unity of the Old and New Testaments, for personal immortality, and the mysterious intercommunion of the visible and invisible worlds. Both meet in Jesus Christ; he is the connecting link between the Old and New Testaments, between heaven and earth, between the kingdom of grace and the kingdom of glory.
It is very significant that at the end of the scene the disciples saw no man save Jesus alive.
Moses and Elijah, the law and the promise, types and shadows, pass away; the gospel, the fulfillment, the substance Christ remains – the only one who can relieve the misery of earth and glorify our nature, Christ all in all. (Mainly taken from Smith’s Larger Bible Dictionary.)