Mark 9:9-13 CSB
As they were coming down the mountain, he ordered them to tell no one what they had seen until the Son of Man had risen from the dead. They kept this word to themselves, questioning what “rising from the dead” meant.
Then they asked him, “Why do the scribes say that Elijah must come first?”
“Elijah does come first and restores all things,” he replied. “Why then is it written that the Son of Man must suffer many things and be treated with contempt? But I tell you that Elijah has come, and they did whatever they pleased to him, just as it is written about him.”
CSB: Christian Standard Bible