Often we speak of the Transfiguration as though it was simply an event in the lives of the three Apostles who were with Jesus, and we conclude they simply misunderstood, and in saying so we move on to the next event in the Gospel narratives. We may conclude that Jesus was in a glorified state, something like we expect him to be at his Second Coming, but then we move on in the narrative. But, wait! What actually happened there on top of Mt. Olives? What did the three Apostles experience, and what might they have been thinking versus its true meaning? What real value can we take away from all this?
I don’t mean to imply that I have all the answers, but I think I know enough to conclude that what the commentaries are telling us can’t be the whole truth either. I think, as a whole, we have concluded we know what the event means, and we’ve moved on without further investigation. Has there been a controversy over this event? Most assuredly so, otherwise, we wouldn’t have at least seven theories about the meaning of Jesus’ words in Luke 9:27. Nevertheless, it seems we have approached the whole event from a mental rather than a heart perspective. We have sought out correct information rather than true meaning. At least this is my perspective, concluded from the limited resources I have, together with my own limited understanding of spiritual matters.
We are told that Jesus took the three disciples up the mountain to pray (Luke 9:28), and as Jesus prayed his countenance was altered (Luke 9:29). Were the disciples supposed to be praying with Jesus, or simply witnessing his prayer? Luke doesn’t tell us, but it seems at least many of us conclude they failed whatever purpose Jesus had in mind, when he brought them apart from the others, because they slept (Luke 9:32). However, Matthew and Mark neither mention that Jesus took the three up the mount to pray, nor that the disciples slept. They simply say the Transfiguration took place before the three disciples and describe that event. Only Luke discloses the disciples initial failure, if, indeed, that’s what it was.
The two men who appeared in glory with Jesus, spoke of his exodus (G1841), which would occur at Jerusalem (Luke 9:31). This same Greek word is used in the Septuagint to describe the exodus of the children of Israel out of Egypt (Exodus 19:1). Again, Luke is the only one of the Synoptics who tells us the subject of Jesus’ conversation with Moses and Elijah. However, were they speaking of Jesus’ death or were they speaking of Jesus’ Ascension into heaven, when he lead captivity captive and gave spiritual gifts to men (Ephesians 4:8; cf. Psalms 68:18)? Both events took place within the suburbs of Jerusalem, and both events could be used to lend meaning to Jesus’ exodus.
I find it striking that the cloud (G3507), out of which the heavenly voice was heard overshadowed (G1982) the three disciples. The Septuagint uses G3507 to point to the pillar of cloud that led Israel through the wilderness (cf. Exodus 13:21) and the Shekinah Glory that represented the presence of God in the Temple (cf. 1Kings 8:10-11). This same cloud overshadowed (G1982) the three disciples, and the Septuagint uses this word to show that, when the cloud overshadowed (G1982) the tent in the wilderness, Moses was unable to enter it (Exodus 40:35). Imagine, Moses was unable to enter the tent in the wilderness (Exodus 40:35), and the priests were unable to perform their duties in the Temple (1Kings 8:10-11), because of the glory of the cloud (Shekinah), yet these three disciples found themselves within this cloud (Shekinah). Why were they able to enter when Moses and the priests of the Temple were excluded?
Moreover, Peter exemplified his confusion over the whole event by asking Jesus, if he should build booths or tents for all three of them (Luke 9:33). Neither was his ignorance improved by being within the cloud (Luke 9:36; cf. Mark 9:10), an experience denied Moses and the priests of the Temple. What does all this mean?
What I gather from this event is this. Many things Jesus told the disciples fell on deaf ears, because they had nothing in their experience to relate his words to. When Jesus spoke of his crucifixion (Luke 9:22), for example, the disciples didn’t know what he meant (Luke 18:31-34), because the Messiah, as far as they knew, couldn’t die (cf. John 12:33-34). What Jesus told them made no sense, and they had no way to categorize such as statement. Therefore, they couldn’t believe.
In my opinion the Transfiguration occurred so the disciples would have an experience to which to look, so they could explain what was occurring to believers, once the Holy Spirit began to dwell within them. Otherwise, they might as well try to imagine a color never before seen that wasn’t based upon red, yellow or blue or a combination of the three. It is just that difficult to imagine a new idea. If the three disciples had no Transfiguration (G3339 – Mark 9:2) to recall, the Holy Spirit would have had nothing to work with to explain how the believer is changed (G3339 – 2Corinthians 3:18) or transformed (G3339) from a worldly likeness to a heavenly likeness (Romans 12:2).
Finally, without a transfigured Jesus (G3339 – Mark 9:2) to look to, John might be able to say: we have no idea what to expect when Jesus appears a second time from heaven, but we’ll probably look differently than we appear now. However, since Jesus was transfigured (G3339 – Mark 9:2), John could say with confidence that we may not know “exactly” what we will look like, but we know this: when Jesus does appear the second time from heaven, we shall look like him, because we shall be able to see him as he is (1John 3:2; cf. 2Corinthians 3:18 and 1John 3:3)!
 See Dr. Bob Utley on Luke 9:27