What does Mark 9:7 mean?
In the Old Testament, God often used a cloud when appearing before His people, most notably the cloud that led the Israelites through the wilderness (Exodus 13:21–22), but also when He met with Moses on Mt. Sinai (Exodus 24:15–18). Jewish scholars call this the shekinah glory of God. "Shekinah" is from the Hebrew meaning "He caused to dwell," and the Shekinah glory is the manifestation of God we can see when He is with us. When faced with this image of glory and the voice of God, Peter, James, and John fall on their faces in terror until Jesus comes to them, touches them, and says, "Rise, and have no fear" (Matthew 17:6–7).This is the second time God affirms His Son. After John the Baptist baptized Jesus, "behold, the heavens were opened to him, and he saw the Spirit of God descending like a dove and coming to rest on him; and behold, a voice from heaven said, 'This is my beloved Son, with whom I am well pleased'" (Matthew 3:16–17).
In the Old Testament, the generic title "son of God" refers to angels and demons (Job 1:6), Nephilim (Genesis 6:2–4), and earthly kings (2 Samuel 7:14). So, while the title is also used of the Messiah (Psalm 80:15), that use is not exclusive. The concept that God would have a physical Son is foreign to Judaism, and not something Peter, James, and John would have understood right away. At most, they would believe God is validating His Messiah, and at least that Jesus is a good, moral man.
God's words "listen to him" explain Moses' presence. In Deuteronomy 18:15, Moses promises the Israelites that God will "raise up for you a prophet like me from among you, from your brothers—it is to him you shall listen…" Peter affirms this is Jesus (Acts 3:22–23).
It is a common claim among unbelievers that they would come to Christ or believe in God if either would show incontrovertible proof of their existence, perhaps just by God speaking to them. Here is evidence that humans are not so constant. Peter, James, and John have traveled with Jesus for months. They have seen His power over storms, illness, and demons. Now, they hear God's own voice validating Jesus and His message. And yet they still can't accept Jesus' clear teaching about what He is there to do as the Messiah (Mark 9:32).
