Mark 9:9-10, 31-32

As they were coming down from the mountain, Jesus expressly ordered them not to tell anyone what they had seen, until the Son of Man had risen from the dead. So they [carefully and faithfully] kept the matter to themselves, discussing and questioning [with one another] what it meant to rise from the dead.

because He was teaching His disciples [and preparing them for the future]. He told them, “The Son of Man is to be betrayed and handed over to men [who are His enemies], and they will kill Him; and when He has been killed, He will rise [from the dead] three days later.” But they did not understand this statement, and they were afraid to ask Him [what He meant].