Numbers 20:25-29

Take Aaron and Eleazar his son, and bring them up unto mount Hor:

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 Moses did as the LORD commanded: and they went up into mount Hor in the sight of all the congregation.

And Moses stripped Aaron of his garments, and put them upon Eleazar his son; and Aaron died there in the top of the mount: and Moses and Eleazar came down from the mount.

And when all the congregation saw that Aaron was dead, they mourned for Aaron thirty days, even all the house of Israel.