Matthew 17:3

καὶ ἰδού introduces a leading and remarkable feature in the scene: ὤφθη αὐτοῖς, there appeared to the three disciples, not necessarily an absolutely real, objective presence of Moses and Elias. All purposes would be served by an appearance in vision. Sufficient objectivity is guaranteed by the vision being enjoyed by all the three, which would have been improbable if purely subjective. Recognition of Moses and Elias was of course involved in the vision. For a realistic view of the occurrence the question arises, how was recognition possible? Euthy. Zig. says the disciples had read descriptions of famous men, including Moses and Elias, in old Hebrew books Another suggestion is that Moses appeared with the law in his hand, and Elias in his fiery chariot. συλλαλοῦντες μ. ἀ., conversing with Jesus, and, it goes without saying (Lk. does say it), on the theme uppermost in all minds, the main topic of recent conversations, the cross; the vision, in its dramatis personæ and their talk, reflecting the state of mind of the seers.