Commentaire sur Le Lévitique 16:4

'כתנת בד וגו [HE SHALL PUT ON] THE LINEN INNER GARMENTS etc. — This teaches us that he must not officiate in the “Interior" (in the Holy of Holies) robed in the eight garments which were the insignia of the High Priest (cf. Exodus 28:4ff) in which he performed the service outside (in the היכל and the עזרה) and in which there was gold interwoven, — because the prosecuting counsel cannot become the defending counsel) — but in the four garments (cf. Exodus 28:40), like an ordinary priest, all of these being on this occasion entirely of linen (whereas one of the four worn by the ordinary priests, the belt, was a mixture of wool and linen) (Rosh Hashanah 26a).

HE SHALL PUT ON THE LINEN TUNIC OF ‘KODESH’ (HOLINESS). “This means that they [i.e., all the garments of the High Priest] must be of the Sanctuary [treasury, and not of his own possession].” This is Rashi’s language.³⁸Rashi thus interprets the verse to mean: “he shall put on the linen tunic of the Sanctuary.” Ramban will later suggest that by way of the simple meaning of Scripture, the phrase means that “he shall put on ‘the holy’ linen tunic.” It is so rendered in the J.P.S. translation. Thus the following phrase which states, they are garments of ‘kodesh’ (holiness) must therefore mean that all the garments [even those of the ordinary priests], must come from the Sanctuary [treasury]. And [so] it is stated in the Torath Kohanim:³⁹Torath Kohanim, Acharei 1:10. “‘Kodesh yilbash’ (‘He shall put on’ the linen tunic ‘of holiness’), this means that these [garments of the High Priest] are to be of the Sanctuary. From this phrase I would only know concerning these garments [i.e., the four garments worn by the High Priest when he ministered in the Holy of Holies on the Day of Atonement]. Whence do I know to include the other garments of the High Priest [i.e., the eight golden garments in which he officiated throughout the year], and the garments of his brethren the priests [that they too must all come from the Temple treasury]? Scripture therefore says, they are garments of ‘kodesh’ (holiness). It is a conclusion by analogy that all garments [worn by all priests] should be of the Temple treasury” [since they all come under the term ‘garments of holiness’].
By way of the simple meaning of Scripture, just as He said, and they shall make holy garments for Aaron thy brother,⁴⁰Exodus 28:4. referring to the eight [golden] garments, He states that these [four garments worn by the High Priest on the Day of Atonement] are also holy garments. Their secret is analogous to the man clothed in linen,⁴¹Ezekiel 9:11. The symbol there is that G-d will not destroy His people, but that He will deal with them in mercy (Abusaula). and therefore He informed him that they are holy garments. And in Vayikra Rabbah the Rabbis have said:⁴²Vayikra Rabbah 21:10. “As the Service performed Above, so is the Service below. Just as of the Service Above it is said, one man in the midst of them clothed in linen,⁴³Ezekiel 9:2. so of the Service below it is said, he shall put on the holy linen tunic.

בגדי קדש הם, when angels appeared in human guise to the prophets they wore these kinds of garments. This is the meaning of the expression לבושי הבדים. (Ezekiel 9,3 and Daniel 12,6-7)