God’s Voice of Approval and Identifying with The Son
Matthew 17:5 (ESV) … “He was still speaking when, behold, a bright cloud overshadowed them, and a voice from the cloud said, “This is my beloved Son, with whom I am well pleased; listen to him.”
Just as God’s voice in the cloud over Mount Sinai gave authority to his law (Exodus 19:9), God’s voice at the Transfiguration gave authority to Jesus’ words. A bright cloud suddenly appeared and overshadowed this group on the mountain. This was not a vapor cloud, but was, in fact, the glory of God. This was the cloud that had guided Israel out of Egypt (Exodus 13:21), that had appeared to the people in the wilderness (Exodus 16:10; 24:15–18; 34:5; 40:34–38), that had appeared to Moses (Exodus 19:9), and that had filled the temple with the glory of the Lord (1 Kings 8:10).
God’s voice spoke from the cloud, singling out Jesus from Moses and Elijah as the long-awaited Messiah who possessed divine authority. As he had done at Jesus’ baptism, the Father was giving verbal approval of his Son (3:17). God was identifying Jesus as the dearly loved Son and the promised Messiah.
God then commanded Peter and the others to hear Jesus, not just their own ideas and desires about what lay ahead. The command recalled the prophecy of Deuteronomy 18:15: “The Lord your God will raise up for you a prophet like me from among your own brothers. You must listen to him” (niv), and it identified Jesus as the Messiah, the fulfillment of that prophecy. The Greek verb akouete, translated “listen,” means not merely hearing, but obeying what is heard.
The voice on the mountain proclaimed Jesus as God’s “beloved Son.” Many images catch sides of Jesus, from classical art to the musical’s Superstar. But at the heart of it, Jesus is God’s beloved Son who deserves our worship and obedience. Not just a friend, more than a moralist, greater than a fearless leader—this is the Christ. Follow him, worship him. 
 Barton, B. B. (1996). Matthew (p. 342). Wheaton, IL: Tyndale House Publishers.