Midrash for Numbers 20:27

6) (Vayikra 8:7) "And he put upon him the kutoneth and he girded him with the avneit, etc." (See Shemoth 29): We are hereby taught that Moses was made an aid to Aaron. And just as he was made his aid in his lifetime, so, he was made his aid in his death. And he would dress him and he would undress him, as it is written (Bamidbar 20:25): "Take Aaron and Elazar his son… (Bamidbar 20:26) and strip Aaron of his vestments, etc." And whence is it derived that Moses did this? From (Bamidbar 20:27): "And Moses did as the L–rd commanded, and they went up to Hor Hahar … (Bamidbar 20:28) and Moses stripped Aaron of his vestments." Now how could Moses strip his vestments in order and dress Elazar in order. Do not the outer garments remain outer garments, and the inner garments remain inner garments? (i.e., We see from Scripture that Aaron did not die until he saw Elazar dressed in the priestly vestments. Is it possible that Aaron stood naked until Elazar donned all the eight vestments?) This transpired miraculously. Variantly: The Holy One Blessed be He accorded him greater honor in his death than in his life. Moses stood him on a rock and stripped him of his priestly vestments, and vestments of the Shechinah clothed him in their stead. Moses stripped his vestments (in order) and clothed Elazar with them in order.

19 (Numb. 20:25-26) “Take Aaron [and his son Elazar] […,] And strip [Aaron]”: The Holy One, blessed be He, said to [Moses], “See, you may console him that he is bequeathing his crown to his sons. [This is] something that you are not bequeathing to your [own] children.” (Numb. 20:28): “So Moses stripped Aaron of his vestments and put them [on his son Elazar].” But if the high priest leaves the Temple mount in priestly vestments, does he not receive forty lashes, since [these vestments] are [made of] wool and flax?⁶⁹Cf. Deut. 22:11, which forbids the mixture, and Kil. 9:1, which allows robes of this mixture for priests when they minister in the Temple. Cf. also Yoma 72a, according to which the forty lashes are for one who tears a priestly garment. However, [Scripture serves] to inform you that, with the wording by which he inducted him into the priesthood, when [the Holy One, blessed be He,] said to [Moses] (in Lev. 8:2), “Take Aaron,” with this very wording He also said to him (in Numb. 20:25), “Take Aaron.” (Numb. 20:27) “So Moses did as the Lord commanded”: [This verse serves] to teach you that, even though He had spoken a decree against Aaron, he did not hesitate.