Matthew 17:9

Tell the vision to no man - This vision was designed particularly to confirm them in the truth that he was the Messiah. While he was with them it was unnecessary that they should relate what they had seen. When he was crucified they would need this evidence that he was the Christ. Then they were to use it. There were three witnesses of it as many as the law required Deuteronomy 17:6; Hebrews 10:28, and the proof that he was the Messiah was clear. Besides, if they had told it then, it would have provoked the Jews and endangered his life. His time was not yet come.

Vision - Sight; appearance. What they had seen on the mount.

Charged them - Gave them a commandment.

The sole design of this transfiguration was to convince them that he was the Christ; that he was greater than the greatest of the prophets; that he was the Son of God.

Mark adds Mark 9:10, “they kept that saying with themselves, questioning one with another what the rising from the dead should mean.” The Pharisees believed that the dead would rise, and there is no doubt that the disciples believed it; but their views were not clear, and, in particular, they did not understand what he meant by his rising from the dead. They do not appear to have understood, though he had told them Mark 12:40 that he would rise after three days.