Remove Aaron’s priestly garments and put them on his son Eleazar. Aaron will be gathered to his people and will die there.”
The chapter began with the funeral of Miriam, and it ends with the funeral of her brother Aaron. When death comes into a family, it often strikes double. Israel had not improved the former affliction they were under, by the death of the prophetess, and therefore, soon after, God took away their priest, to try if they would lay that to heart.
Commenting on Numbers 20:22-29
And Moses did as the Lord commanded,.... Though it must be very cutting, distressing, and afflicting to him, to part with a brother so dear to him, and who had been so many years a companion of him, and a partner with him in the care and government of the people of Israel; but it being the Lord's will, he submits unto it, and faithfully...
strip Aaron of his garments--that is, his pontifical robes, in token of his resignation. (See Isa 22:20-25). put them on his son--as the inauguration into his high office. Having been formerly anointed with the sacred oil, that ceremony was not repeated, or, as some think, it was done on his return to the camp.