Jesus warned His followers that He would soon be killed by the leaders (Matthew 16:21). His closest disciples were sad when they heard this. God chose this time to prove to them, beyond any doubt, the truth about Jesus.
And after six days Jesus took with him Peter and James, and John his brother, and led them up a high mountain by themselves. And he was transfigured [changed] before them, and his face shone like the sun, and his clothes became white as light (Matthew 17:1-2).
Though still a Man, He shone with glory far beyond anything human. Even His clothing “became dazzling [very bright] white” (Luke 9:29). You may have seen lightning, or looked into the shining sun. If so, you have an idea of the glory of Jesus’ body and face. This was what Peter meant when he said,
“We were eyewitnesses of His majesty” (2 Peter 1:16).
God had already shown Jesus to be the spiritual and moral “light of the world.” To this God now added visible proof of Jesus’ own heavenly light. Then God gave His proof from heaven. He sent Moses (the lawgiver) and Elijah (the great prophet) to appear in glory beside Jesus. Peter wanted to honor all three, but God honored only Jesus.
He [Peter] was still speaking when, behold, a bright cloud overshadowed [covered] them, and a voice from the cloud said, “This is my beloved Son, with whom I am well pleased; listen to him!” (Matthew 17:5).