Numbers 20:27-31

So Moses did just as the Lord had commanded, and they went up to Mount Hor in the sight of all the congregation.

And after Moses stripped Aaron of his garments and put them on his son Eleazar, Aaron died there on the mountain top. Then Moses and Eleazar came down from the mountain.

When all the congregation saw that Aaron had died, the whole house of Israel wept for Aaron for thirty days.