Jesus and three of His disciples have been on Mt. Hermon, where He was transfigured before them -- assuming the appearance that He will bear in the coming age. Moses and Elijah have appeared there -- conversing with Him concerning His coming decease at Jerusalem. That sight, and the voice of the Father which spoke out of the overshadowing cloud, had filled the disciples with fear and awe. Thus, they fell on their faces. But Jesus came and touched them, saying: "Arise, and be not afraid". And when they had lifted up their eyes, they saw no man, save Jesus only, (Matt. 17:10-13; Lk. 9:11-13).
As they descended the mountain, the Master charged them, saying: "Tell the vision to no man until the Son of Man be risen again from the dead". Therefore, they kept this saying to themselves -- questioning one another concerning its meaning.
Puzzled by the appearance of Elijah, they asked the Master, "Why then say the scribes that. Elias must first come"! (comp. Mal. 3:1; 4:5-6; Isa. 40:1-5).