The Transfiguration is the event when Christ’s two natures are made clearly visible. In front of human witnesses – Christ exchanges his temporal earthly form for his eternal divine form for a moment…
The Transfiguration was not a phenomenon circumscribed in time and space; Christ underwent no change at that moment, even in His human nature – the change occurred in the awareness of the apostles, who for a time received the power to see their Master as He was, resplendent in the eternal light of the Godhead. The light which Christ radiated on Mount Tabor is eternal and is visible through reflection, introspection and the silence of inward prayer – waiting upon God in emptiness and quietness.
The Transfiguration is one of the greatest mysteries of the Christian revelation, and one that is important to icon painters – it gives us permission to attempt to portray the divine light of God – which is in the likeness of Christ. A mystery is something that while it may be revealed for our understanding, we can never understand it exhaustively. It leads us into the depth, and into the darkness of God. The eyes are closed – but they are also opened.
And Christ was transfigured before them (Peter, James and John): and his face did shine as the sun, and his raiment was as white as the light. …[Peter then expressed how good it was to be there and suggested perhaps they build some sort of altar] … While he yet spake, behold, a bright cloud overshadowed them: and behold a voice out of the cloud, which said, This is my beloved Son, in whom I Am well pleased; hear ye him. And when the disciples heard it, they fell on their faces and were sore afraid,” (Matt 17:2-7, Mark 9:2-13, Luke 9:28-36)