Adam Clarke on Numbers 20:26

Strip Aaron of his garments - This was, in effect, depriving him of his office; and putting the clothes on his son Eleazar implied a transfer of that office to him. A transfer of office, from this circumstance of putting the clothes of the late possessor on the person intended to succeed him, was called investing or investment, (clothing); as removing a person from an office was termed divesting or unclothing. Among the Catholics, and in the Church of England, this same method is used in degrading ecclesiastics. Hence such a degradation is termed by the common people stripping a man of his gown.