And after six days Jesus taketh unto him Peter and James, and John his brother, and bringeth them up into a high mountain apart: And he was transfigured before them. And his face did shine as the sun: and his garments became white as snow. And behold there appeared to them Moses and Elias talking with him. And Peter answering, said to Jesus: "Lord, it is good for us to be here: if thou wilt, let us make here three tabernacles, one for thee, and one for Moses, and one for Elias." And as he was yet speaking, behold a bright cloud overshadowed them. And lo a voice out of the cloud, saying: "This is my beloved Son, in whom I am well pleased: hear ye him." And the disciples hearing fell upon their face, and were very much afraid. And Jesus came and touched them: and said to them: "Arise, and fear not." And they lifting up their eyes, saw no one, but only Jesus. And as they came down from the mountain, Jesus charged them, saying: "Tell the vision to no man, till the Son of man be risen from the dead." (Matt. 17:1-9)
JESUS IS THE MESSIAH AND LAWGIVER OF THE NEW TESTAMENT: The apparition of Moses and Elias proved Jesus to be the Messiah to whom the law and the prophets pointed. They paid homage to Him as their Lord, Who had fulfilled the law and the prophets, and Who by His impending death would release the holy men of the Old Covenant from Limbo, and admit them into heaven. The voice of the heavenly Father proclaimed Jesus to be the Founder and Lawgiver of the New Covenant, the teaching of which all men are bound to believe, and the commandments of which they are bound to obey. This narrative, therefore, reveals Jesus to us as the Messiah, and the Fulfiller of the law and the prophets, the Divine Founder and Lawgiver of the New Covenant, the Redeemer of mankind in all ages, and the center of the history of the world.
[From 'A Practical Commentary on Holy Scripture' by Bishop Knecht, D.D.]
(1899 Douay-Rheims Bible)