This is a euphemism that means Moses will die and his spirit will go to the place where his ancestors are. Alternate translation: "you must die" (See: [[rc://en/ta/man/translate/figs-euphemism]])
You can make clear the understood information that Aaron died. Alternate translation: "and you must die like your older brother Aaron died" (See: [[rc://en/ta/man/translate/figs-ellipsis]] and [[rc://en/ta/man/translate/figs-explicit]])