And behold there appeared unto them Moses and Elias - Moses, a distinguished servant of God, by whom the law was given, and whose institutions typified the Messiah. It was particularly proper that he should appear, when his prophecies and types were about to be fulfilled, and the rites which he had instituted were about to be done away. Elias, or Elijah, a distinguished prophet, taken to heaven without seeing death. See 2 Kings 2:11. Elijah had been honored eminently by being thus translated, and still more by being made the model of the forerunner of the Messiah, Malachi 4:5; Luke 1:17; Matthew 11:14. They appeared “in glory” Luke 9:31; i. e., as they are in heaven with the glory which the redeemed have there.
Talking with him - Luke Luke 9:31 informs us that they conversed about “his decease which he should accomplish at Jerusalem.” To redeemed spirits that death was an object of intense interest. By faith in that death they had been saved; and now that the Redeemer of mankind was about to die, it is no wonder that this was the burden of his and their thoughts.
Luke adds Luke 9:32 that “Peter and they that were with him were heavy with sleep.” It is not improbable that this was in the night; that Jesus was engaged in prayer; and that he had permitted his weary followers to compose themselves to rest. It was after they were awaked that they saw this vision. Probably the sudden splendor, the bright shining aroused them from sleep.