This can be stated in active form. Alternate translation: "Aaron must wear the robe when he serves" (See: [[rc://en/ta/man/translate/figs-activepassive]])
It is implied that he would die because he did not obey Yahweh. This can be stated. Alternate translation: "As a result, he will not die because of disobeying my instructions" (See: [[rc://en/ta/man/translate/figs-explicit]])