5 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.
Chrysostom: When the Lord threatens, He shews a dark cloud, as on Sinai [Exod 19:9]; but here where He sought not to terrify but to teach, there appeared a bright cloud.
Origen: The bright cloud overshadowing the Saints is the Power of the Father, or perhaps the Holy Spirit; or I may also venture to call the Saviour that bright cloud which overshadows the Gospel, the Law, and the Prophets, as they understand who can behold His light in all these three.
Chrysostom: Fear not then, Peter; for if God is mighty, it is manifest that the Son is also mighty; wherefore if He is loved, fear not thou; for none forsakes Him whom He loves; nor dost thou love Him equally with the Father. Neither does He love Him merely because He begot Him, but because He is of one will with Himself; as it follows, “In whom I am well pleased;” which is to say, in whom I rest content, whom I accept, for all things of the Father He performs with care, and His will is one with the Father; so if He will to be crucified, do not then speak against it.
Remigius: He says therefore, “Hear Him,” as much as to say, Let the shadow of the Law be past, and the types of the Prophets, and follow ye the one shining light of the Gospel. Or He says, “Hear ye Him,” to shew that it was He whom Moses had foretold, “The Lord your God shall raise up a Prophet unto you of your brethren like unto me, Him shall ye hear.” [Deut 18:18]
Origen: The voice out of the cloud speaks either to Moses or Elias, who desired to see the Son of God, and to hear Him; or it is for the teaching of the Apostles.
Gloss: The mystery of the second regeneration, that, to wit, which shall be in the resurrection, when the flesh shall be raised again, agrees well with the mystery of the first which is in baptism, when the soul is raised again. For in the baptism of Christ is shewn the working of the whole Trinity; there was the Son incarnate, the Holy Ghost appearing in the figure of a dove, and the Father made known by the voice. In like manner in the transfiguration, which is the sacrament of the second regeneration, the whole Trinity appeared; the Father in the voice, the Son in the man, and the Holy Spirit in the cloud. It is made a question how the Holy Spirit was shewn there in the dove, here in the cloud. Because it is His manner to mark His gifts by specific outward forms. And the gift of baptism is innocence, which is denoted by the bird of purity. But as in the resurrection, He is to give splendour and refreshment, therefore in the cloud are denoted both the refreshment and the brightness of the rising bodies.
Scripture from the Douay-Rheims Bible. Commentary from St. Thomas Aquinas, Catena Aurea, Vol. I (London: Rivington, 1842).