Matthew 17:3

"Behold" again introduced something amazing (cf. Matthew 1:20; Matthew 2:13; et al.). Matthew probably mentioned Moses first because to the Jews he was the more important figure. Moses was the model for the eschatological Prophet whom God would raise up, specifically, Messiah (Deuteronomy 18:18). Elijah was the prophesied forerunner of Messiah (Malachi 4:5-6; cf. Matthew 3:1-3; Matthew 11:7-10; Matthew 17:9-13). Both prophets had unusual ends. Perhaps Moses represented those who will be in the kingdom who had died and Elijah those whom God had translated. [Note: Walvoord, Matthew: . . ., p. 130.] The disciples may represent those there who had not died. [Note: Barbieri, p. 59.]

Both Moses and Elijah played key roles in God’s plan for Israel. Moses established the (Mosaic) covenant under which Israel proceeded to live, and Elijah led the people back to that covenant and God after their worst apostasy. Both experienced a vision of God’s glory on a mountain. Both experienced rejection by Israel (Acts 7:35; Acts 7:37; 1 Kings 19:1-9; cf. Matthew 17:12). Moses was the greatest figure associated with the law, and Elijah was arguably the greatest of the Old Testament prophets. The disciples would later learn that Jesus was greater than either of these great men (Matthew 17:5; Matthew 17:8). However now the disciples saw Moses and Elijah talking with Jesus.

"The abiding validity of the Law and the Prophets as ’fulfilled’ by Christ (Mt. Matthew 17:17) is symbolized by the harmonious converse which He holds with their representatives, Moses and Elijah." [Note: M’Neile, p. 251.]