Adam Clarke on Matthew 17:2

Was transfigured - That fullness of the Godhead, which dwelt bodily in Christ, now shone forth through the human nature, and manifested to his disciples not only that Divinity which Peter had before confessed, Mat 16:16, but also the glorious resurrection body, in which they should exist in the presence of God to eternity.

White as the light - But the Cod. Bezae, some of the ancient versions, and several of the fathers, read ως χιων, as snow; and this is the reading in Mar 9:3.