Numbers 20:26
And strip Aaron of his garments, and put them upon Eleazar his son: and Aaron shall be gathered unto his people, and shall die there. And strip Aaron of his garments, and put them upon Eleazar his son: and Aaron shall be gathered unto his people, and shall die there.
Numbers 20:26 belongs to the directions for Aaron's death on Mount Hor, where he was to die and be gathered to his people. He died there without entering the promised land because he and Moses sinned when bringing water from the rock at Meribah. His priestly garments were to be stripped from him and put upon his son Eleazar, marking Eleazar's succession to the priesthood and sacred office.
Moses himself was to perform the painful duty of removing the sacerdotal robes and placing them on Eleazar, because God had appointed Eleazar to succeed Aaron. Moses and Eleazar witnessed Aaron's death, and Moses buried him on the mount in their presence. Moses with Aaron's sons buried him on the mountain. That burial on the mountain kept the people from making excessive ceremony over his body and falling into idolatry.
The scene on Mount Hor, with Aaron dying and being buried there in the presence of his brother Moses and his son Eleazar, links back to the most striking events in Aaron's life.