"sn In 1st century Judaism and in the NT, it was believed that the righteous would be given new, glorified bodies in order to enter heaven (cf. 1 Cor 15:42-49; 2 Cor 5:1-10). This transformation meant that the righteous will share the glory of God. The account of Jesus’ transfiguration here recalls the way Moses shared the Lord’s glory after his visit to the mountain in Exod 34:28-35. So the disciples saw Jesus transfigured, and they were getting a private preview of the great glory that Jesus would have following his exaltation."
But how could Peter, James, and John recognize Moses when they never encountered him previously? How did they know that the two mysterious figures were actually Moses and Elijah? They could have appeared with Christ in a manner that the disciples could identify. Scripture does not supply us with a tome of information concerning the "mechanics" of the soul.
God announced His approval of Jesus Christ from heaven (Matthew 17:5-6). He is the perfect and acceptable sacrifice for sin. Christ will restore peace and reign for eternity as the King of kings and Lord of lords. Stephen N. Williams gives the following commentary on the Transfiguration:
"There may be reminders or echoes of the scene of transfiguration elsewhere in the NT, of course; the stories of Paul’s own conversion, in the Book of Acts that combine Jesus, light and a voice from heaven; the very rare (NT) word ‘transfigure’ is the one used by Paul when he tells the Corinthians that we ‘are being transformed [‘transfigured’] into his likeness with ever-increasing glory’ (2 Cor. 3:18); the first chapter of Revelation, with its dramatic portrayal of Jesus, has resonances. John’s Gospel is intriguing on this score. It contains no reference to the transfiguration, but it is a Gospel all about ‘glory’ and a voice from heaven thunders that God has glorified his name ‘and will glorify it again’ (12:28). The question about why John does not specifically mention transfiguration belongs to the wider discussion of its relationship to the Synoptics. We must bear in mind that John does not refer directly to the Last Supper either or directly report the actual baptism of Jesus, where the Synoptics do. John can be concerned with the surrounding interpretation of events that he does not report as do the Synoptists."