And strip Aaron of his garments and put them on Eleazar his son. And Aaron shall be gathered to his people and shall die there.
Numbers 20:26 #chukat

The High Priest shouldn't be allowed to die in office. A successor should be appointed long before his death becomes likely and he should retire.

If a function is vital to the health of the people (e.g. priest, king, pastor, judge, PRESIDENT, etc), only a self-centered person who has forgotten why he serves would neglect to provide for a peaceful and smooth transition.