“What does it mean to say: He was transfigured?” asks the Golden-Mouthed Theologian (Chrysostomos). He answers this by saying: “It revealed something of His Divinity to them, as much and insofar as they were able to apprehend it, and it showed the indwelling of God within Him.” The Evangelist Luke says: “And as He prayed, His countenance was altered” (Lk 9:29); and from the Evangelist Matthew we read: “And His face shone as the sun” (Mt 17:2). But the Evangelist said this, not in the context that this Light be thought of as subsistent for the senses (let us put aside the blindness of mind of those who can conceive of nothing higher than what is known through the senses). Rather, it is to show that Christ God, for those living and contemplating by the Spirit, is the same as the sun is for those living in the flesh and contemplating by the senses. Therefore, some other Light for the knowing the Divinity is not necessary for those who are enriched by Divine gifts.
-St. Gregory Palamas on Transfiguration