Matthew 17:3

Moses and Elias - Elijah came from heaven in the same body which he had upon earth, for he was translated, and did not see death, 2 Kings 2:11. And the body of Moses was probably raised again, as a pledge of the resurrection; and as Christ is to come to judge the quick and the dead, for we shall not all die, but all shall be changed, 1 Corinthians 15:51, he probably gave the full representation of this in the person of Moses, who died, and was thus raised to life, (or appeared now as he shall appear when raised from the dead in the last day), and in the person of Elijah, who never tasted death. Both their bodies exhibit the same appearance, to show that the bodies of glorified saints are the same, whether the person had been translated, or whether he had died. It was a constant and prevalent tradition among the Jews, that both Moses and Elijah should appear in the times of the Messiah, and to this very tradition the disciples refer, Matthew 17:10.

We may conceive that the law in the person of Moses, the great Jewish legislator, and the prophets in the person of Elijah, the chief of the prophets, came now to do homage to Jesus Christ, and to render up their authority into his hands; as he was the End of the law, and the grand subject of the predictions of the prophets. This appears more particularly from what St. Luke says, Luke 9:31, that Moses and Elijah conversed with our Lord on his death, which he was about to accomplish, (πληρουν to fulfill), because in it, all the rites, ceremonies, and sacrifices of the law, as well as the predictions of the prophets, were fulfilled.

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 Luk 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.

17:3 There appeared Moses and Elijah - Here for the full confirmation of their faith in Jesus, Moses, the giver of the law, Elijah, the most zealous of all the prophets, and God speaking from heaven, all bore witness to him.