The clarity of the glorified body is derived from that of the soul

Summa:
The clarity which Christ assumed in His transfiguration was the clarity of glory as to its essence, but not as to its mode of being. For the clarity of the glorified body is derived from that of the soul, as Augustine says (Ep. ad Diosc. cxviii). And in like manner the clarity of Christ's body in His transfiguration was derived from His God. head, as Damascene says (Orat. de Transfig.) and from the glory of His soul. That the glory of His soul did not overflow into His body from the first moment of Christ's conception was due to a certain Divine dispensation, that, as stated above (Question [14], Article [1], ad 2), He might fulfil the mysteries of our redemption in a passible body. This did not, however, deprive Christ of His power of outpouring the glory of His soul into His body. And this He did, as to clarity, in His transfiguration, but otherwise than in a glorified body. For the clarity of the soul overflows into a glorified body, by way of a permanent quality affecting the body. Hence bodily refulgence is not miraculous in a glorified body. But in Christ's transfiguration clarity overflowed from His Godhead and from His soul into His body, not as an immanent quality affecting His very body, but rather after the manner of a transient passion, as when the air is lit up by the sun. Consequently the refulgence, which appeared in Christ's body then, was miraculous: just as was the fact of His walking on the waves of the sea. Hence Dionysius says (Ep. ad Cai. iv): "Christ excelled man in doing that which is proper to man: this is shown in His supernatural conception of a virgin and in the unstable waters bearing the weight of material and earthly feet."

Image