The Transfiguration of Our Lord, God and Savior Jesus Christ
What does "transfiguration" mean?
Christ was transfigured, not by the addition of something He was not, nor by a transformation into something He was not, but by the manifestation to His disciples of what He really was.
He opened their eyes so that instead of being blind they could see. While He Himself remained the same, they could now see Him as other than He had appeared to them formerly. For He is ‘the true light’ (Jn 1:9), the beauty of divine glory, and He shone forth like the sun—though this image is imperfect, since what is uncreated cannot be imaged in creation without some diminution.
St. Gregory Palamas,
Archbishop of Thessaloniki
Hymn for the Transfiguration
You were transfigured upon the mountain O Christ our God, showing to Your disciples Your glory as much as they could bear. Do also in us, sinners though we be, shine Your everlasting Light. At the intercessions of the Theotokos, O Giver of Light, glory to You.