This phrase gives information about how Moses and Elijah looked. Some languages would translate it as a separate clause. AT: "and they appeared in glorious splendor" or "and they were shining brightly" (See: [[rc://en/ta/man/translate/figs-distinguish]])
"his leaving" or "how Jesus would leave this world." This was a polite way of talking about his death. AT: "his death" (See: [[rc://en/ta/man/translate/figs-euphemism]])