The more I review this passage, the more interest I have in understanding how Protestants in particular explain it:
1: And after six days Jesus taketh Peter, James, and John his brother, and bringeth them up into an high mountain apart,
2: And was transfigured before them: and his face did shine as the sun, and his raiment was white as the light.
3: And, behold, there appeared unto them Moses and Elias talking with him.
4: Then answered Peter, and said unto 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.
5: While he yet spake, behold, a bright cloud overshadowed them: and behold a voice out of the cloud, which said, This is my beloved Son, in whom I am well pleased; hear ye him.
6: And when the disciples heard it, they fell on their face, and were sore afraid.
7: And Jesus came and touched them, and said, Arise, and be not afraid.
8: And when they had lifted up their eyes, they saw no man, save Jesus only.
9: And as they came down from the mountain, Jesus charged them, saying, Tell the vision to no man, until the Son of man be risen again from the dead.
10: And his disciples asked him, saying, Why then say the scribes that Elias must first come?
11: And Jesus answered and said unto them, Elias truly shall first come, and restore all things.
12: But I say unto you, That Elias is come already, and they knew him not, but have done unto him whatsoever they listed. Likewise shall also the Son of man suffer of them.
13: Then the disciples understood that he spake unto them of John the Baptist.
The reason I find it so interesting is that here we have Moses and Elijah, from days long past, conversing with Jesus. We have Peter, foremost among the apostles, offering to honor them by building tabernacles for sukot, the Jewish holiday given prominence by Moses himself in a past age, an honor bestowed typically upon members of one’s family.
I have wondered why Moses and Elijah were present. This passage from the Catechism may provide a clue:
2583 After Elijah had learned mercy during his retreat at the Wadi Cherith, he teaches the widow of Zarephath to believe in The Word of God and confirms her faith by his urgent prayer: God brings the widow’s child back to life.
The sacrifice on Mount Carmel is a decisive test for the faith of the People of God. In response to Elijah’s plea, “Answer me, O LORD, answer me,” the Lord’s fire consumes the holocaust, at the time of the evening oblation. The Eastern liturgies repeat Elijah’s plea in the Eucharistic epiclesis.
Finally, taking the desert road that leads to the place where the living and true God reveals himself to his people, Elijah, like Moses before him, hides “in a cleft of he rock” until the mysterious presence of God has passed by. But only on the mountain of the Transfiguration will Moses and Elijah behold the unveiled face of him whom they sought; “the light of the knowledge of the glory of God [shines] in the face of Christ,” crucified and risen.
For the Catholic, the Transfiguration is a beautiful example of the communion of the saints, and an evocation of what eternal life really means.
For those who do not believe in the communion of the saints, or even that to speak to the dead (as Moses at least surely was) is an abomination, this passage begs for interpretation.
I am doing some research myself on the subject, but perhaps someone has a ready explanation they could share.