When the voice finished, Jesus was there alone. They didn’t tell anyone at that time what they had seen.
A time to tear and a time to mend. A time to be quiet and a time to speak.
As they went back down the mountain, Jesus commanded them, “Don’t tell anyone what you have seen until the Son of Man has been raised from the dead.”
He said this because he didn’t really know what else to say, for they were all terrified.