Numbers 20:23-28

20:23 And the Lord spoke to Moses and Aaron in Mount Hor, by the border of the land of Edom. He said: 20:24 “Aaron will be gathered to his ancestors, for he will not enter into the land I have given to the Israelites because both of you rebelled against my word at the waters of Meribah. 20:25 Take Aaron and Eleazar his son, and bring them up on Mount Hor. 20:26 Remove Aaron’s priestly garments and put them on Eleazar his son, and Aaron will be gathered to his ancestors and will die there.”

20:27 So Moses did as the Lord commanded; and they went up Mount Hor in the sight of the whole community. 20:28 And Moses removed Aaron’s garments and put them on his son Eleazar. So Aaron died there on the top of the mountain. And Moses and Eleazar came down from the mountain.

Numbers 33:38

33:38 Aaron the priest ascended Mount Hor at the command of the Lord, and he died there in the fortieth year after the Israelites had come out of the land of Egypt on the first day of the fifth month.