Origen

Mystically; When any one has passed the six days according as we have said, he beholds Jesus transfigured before the eyes of his heart. For the Word of God has various forms, appearing to each man according as He knows that it will be expedient for him; and He shews Himself to none in a manner beyond his capacity; whence he says not simply, He was transfigured, but, before them. For Jesus, in the Gospels, is merely understood by those who do not mount by means of exalting works and words upon the high mountain of wisdom; but to them that do mount up thus, He is no longer known according to the flesh, but is understood to be God the Word. Before these then Jesus is transfigured, and not before those who live sunk in worldly conversation. But these, before whom He is transfigured, have been made sons of God, and He is shewn to them as the Sun of righteousness. His raiment is made white as the light, that is, the words and sayings of the Gospels with which Jesus is clothed according to those things which were spoken of Him by the Apostles.