“And as he prayed, the fashion of his countenance was altered, and his raiment was white and glistering.”
Luke 9:29 — Greek Interlinear
Church Fathers on Luke 9:29
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 eight days after these sayings, he took Peter and John and James, and went up into a mountain to pray.
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…
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.