Matthew 17:9
And as they came down from the mountain, Jesus charged them, saying, Tell the vision to no man, until the Son of man be risen again from the dead. And as they came down from the mountain, Jesus charged them, saying, Tell the vision to no man, until the Son of man be risen again from the dead.
As they came down from the mountain of transfiguration, Peter, James and John were charged to tell the vision of His glory to no one until after the Son of man had risen from the dead. The command came after they had fallen on their faces sore afraid at the voice from the cloud, after Jesus had come and touched them and said arise and be not afraid, and after they had lifted their eyes and seen no man save Jesus only. It followed Peter's troubled proposal to make three tabernacles, which sought to keep Jesus at a safe distance on the mountain and escape death on the cross. Instead of publishing what they had seen, the three were to ponder the revelation in private.
Silence was required because neither the crowds nor the other disciples were yet prepared to appreciate or understand what had been witnessed. To have made the vision public beforehand would have invited ridicule from some and mere idle wonder from others. Even the three favored disciples themselves did not understand what rising from the dead meant, although Jesus had spoken of what lay ahead. The vision belonged to future scenes that would only be understood in the light of His resurrection.
The mountain manifestation of His divinity gave them proof they could not doubt that He is the promised Messiah and Son of God, with God's voice declaring His divinity and Moses and Elijah paying Him homage, and it was meant to remove their doubts. That assurance was meant to sustain and strengthen them through His coming humiliation and death and crucifixion, showing that His death was part of God's plan of redemption. After His resurrection their eyewitness testimony was to confirm and prove that He is indeed the Son of God.
To have stood with Christ on the mount is to have seen His glory, with the glory of the Lord risen upon the spirit until the soul beholding His beauty as chiefest among ten thousand and altogether lovely becomes radiant in His presence. That experience sends His followers down from the mount into the valley and plain where demon-possessed souls enslaved by Satan wait for the word of faith and prayer to set them free. Those who have received this light are sent by the word of the Master to arise and shine, to live and labor and sacrifice even unto death for the saving of humanity in Christ's self-sacrificing love.