Numbers 20:25 Take Aaron and Eleazar his son, and bring them up unto mount Hor: 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. 27 And Moses did as the LORD commanded: and they went up into mount Hor in the sight of all the congregation. 28 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. 29 And when all the congregation saw that Aaron was dead, they mourned for Aaron thirty days, even all the house of Israel.
Aaron’s garments were those specially made for the High Priest.
Exodus 28:2 And thou shalt make holy garments for Aaron thy brother for glory and for beauty. (read on to verse 39)
With Aaron’s death Eleazar became the High Priest and the garments were put upon him.
Exodus 29:29 And the holy garments of Aaron shall be his sons’ after him, to be anointed therein, and to be consecrated in them. 30 And that son that is priest in his stead shall put them on seven days, when he cometh into the tabernacle of the congregation to minister in the holy place.
We might reasonably suppose that the thing was done in the sight of all the congregation of Israel so that there would be no doubt that Aaron’s office had been passed on to Eleazar at the commandment of God.
The transaction is seen in the English language when one is said to be ‘invested’ [given the official vestments] in office. When one is removed from office the terms ‘divested’ or (in clerical circles) ‘defrocked’ are used.
I hope you have found this helpful.
God bless you,