Mark 9:2-10 Revised Standard Version Catholic Edition (RSVCE)
2 And after six days Jesus took with him Peter and James and John, and led them up a high mountain apart by themselves; and he was transfigured before them, 3 and his garments became glistening, intensely white, as no fuller on earth could bleach them. 4 And there appeared to them Eli′jah with Moses; and they were talking to Jesus. 5 And Peter said to Jesus, “Master,[a] it is well that we are here; let us make three booths, one for you and one for Moses and one for Eli′jah.” 6 For he did not know what to say, for they were exceedingly afraid. 7 And a cloud overshadowed them, and a voice came out of the cloud, “This is my beloved Son;[b] listen to him.” 8 And suddenly looking around they no longer saw any one with them but Jesus only.
The Coming of Elijah
9 And as they were coming down the mountain, he charged them to tell no one what they had seen, until the Son of man should have risen from the dead. 10 So they kept the matter to themselves, questioning what the rising from the dead meant.