Luke 9:28

Our Lord, when He made known to His disciples the great mystery of His second coming, that it might not seem that they were to believe in His words only, proceeds to works, manifesting to them, through the eyes of their faith, the image of His kingdom; as it follows, And it came to pass about an eight days after these sayings, he took Peter and John and James, and went up into a mountain to pray.

Or, Peter went up, who received the keys of the kingdom of heaven; John, to whom was committed our Lord's mother; James, who first suffered martyrdom. (Acts 12:1.) Now in a mystical manner, after the words above said, is exhibited the transfiguration of Christ, since he who hears the words of Christ, and believes, shall see the glory of His resurrection. For, on the eighth day the resurrection took place. Hence also several Psalms are written, 'for the eighth,' (pro octava.) or perhaps it was that He might make manifest what He had said, that he who for the word of God shall lose his own life, shall save it, seeing that He will make good His promises at the resurrection. But Matthew and Mark have related that He took them with Him after six days, of which we may say after 6000 years, (for a thousand years in the Lord's sight are as one day;) but more than 6000 years are reckoned. We had rather then take the six days symbolically, that in six days the works of the world were completed, that by the time we may understand the works, by the works the world. And so the times of the world being finished, the resurrection to come is declared; or because, He who has ascended above the world, and has passed beyond the moments of this life, is waiting, seated as it were on a high place, for the everlasting fruit of the resurrection. I should think that in the three who are taken up into the mountain, was contained in a mystery the human race, because from the three sons of Noah sprung the whole race of man; I did not perceive that they were chosen out. Three then are chosen to ascend the mountain, because none can see the glory of the resurrection, but they who have preserved the mystery of the Trinity with inviolable purity of faith.

Not as though His body changed its human form, but a certain glistening glory overspread it.

For as He rose from the dead after the seventh day of the Sabbath, during which He lay in the tomb, we also after the six ages of this world, and the seventh of the rest of souls, which meanwhile is passed in another life, shall rise again as it were in the eighth age. Hence He ascends the mountain to pray and be transfigured, to show that those who expect the fruit of the resurrection, and desire to see the King in His glory, ought to have the dwelling place of their hearts on high, and be ever on their knees in prayer.

(Orat. de Trans fig. §. 8.) Matthew and Mark indeed say that the transfiguration took place on the sixth day after the promise made to the disciples, but Luke on the eighth. But there is no disagreement in these testimonies, but they who make the number six, taking off a day at each end, that is, the first and the last, the day on which He makes the promise, and that on which He fulfilled it, have reckoned only the intervening ones, but He who makes the number eight, has counted in each of the two days above mentioned. But why were not all called, but only some, to behold the sight? There was only one indeed who was unworthy to see the divinity, namely Judas, according to the word of Isaiah, Let the wicked be taken away, that he should not behold the glory of God. (Isai. 26:10 LXX.) If then he alone had been sent away, he might have, as it were from envy, been provoked to greater wickedness. Henceforward He takes away from the traitor every pretext for his treachery, seeing that He left below the rest of the company of the Apostles. But He took with Him three, that in the mouths of two or three witnesses every word should be established. He took Peter, indeed, because He wished to show him that the witness he had borne to Him was confirmed by the witness of the Father, and that he was as it were to preside over the whole Church. He took with Him James, who was to be the first of all the disciples to die for Christ; but He took John as the clearest singer of the sacred doctrine, that having seen the glory of the Son, which submits not to time, he might sound forth, In the beginning was the Word. (John 1:1.)