“As they were coming down
The mountain,
He ordered them
To tell no one
About what they had seen,
Until the Son of Man
Had been raised
From the dead.”
Καὶ καταβαινόντων αὐτῶν ἐκ τοῦ ὄρους διεστείλατο αὐτοῖς ἵνα μηδενὶ ἃ εἶδον διηγήσωνται, εἰ μὴ ὅταν ὁ Υἱὸς τοῦ ἀνθρώπου ἐκ νεκρῶν ἀναστῇ.
Once again, we are back at the messianic secret that can be found in all 3 synoptic gospels, Matthew, chapter 16:9, Luke, chapter 9:36, and here in Mark that is closer to Matthew. Jesus and his 3 disciples came down or descended from the mountain (Καὶ καταβαινόντων αὐτῶν ἐκ τοῦ ὄρους). He admonished, commanded, instructed, or ordered them (διεστείλατο αὐτοῖς) not to tell anyone about what they had seen (ἵνα μηδενὶ ἃ εἶδον διηγήσωνται) until the Son of Man had been raised from the dead (εἰ μὴ ὅταν ὁ Υἱὸς τοῦ ἀνθρώπου ἐκ νεκρῶν ἀναστῇ). They would be free to speak about this after the death and resurrection of Jesus, but not before that turning point among the followers of Jesus.