Numbers 20:27-29 New King James Version (NKJV)

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

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

29. Now when all the congregation saw that Aaron was dead, all the house of Israel mourned for Aaron thirty days.

Numbers 20