Leviticus 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). קדש ילבש HE SHALL PUT ON [THE LINEN INNER GARMENT] OF HOLINESS (or, OF THE SANCTUARY) - This means that they shall be purchased from the Temple treasury (whilst his personal offering mentioned v. 3 had to be of his own) (Sifra, Acharei Mot, Chapter 1 10). יצנף — Understand this as the Targum does: יחת ברישה which means: he shall place upon his head. Thus, the verb in (Genesis 39:16) ותנח בגדו, is rendered by the Targum ואחתתיה (of the same root as יחת) “and she placed". ורחץ במים AND HE SHALL LAVE [HIS FLESH] IN WATER — That day he required immersion at each change of his garments! Five times he proceeded alternately from the service in the “Interior" to that performed outside and from the outside service to that in the "Interior", changing from the golden garments into the linen garments or from the linen garments into the golden garments. At each change he required to take an immersion and to wash his hands and his feet twice from the laver (viz., before he took off the garments he was wearing and after he had put on others — in all, 10 times during the day) (Yoma 32a).

כְּתֹֽנֶת־בַּ֨ד קֹ֜דֶשׁ יִלְבָּ֗שׁ וּמִֽכְנְסֵי־בַד֮ יִהְי֣וּ עַל־בְּשָׂרוֹ֒ וּבְאַבְנֵ֥ט בַּד֙ יַחְגֹּ֔ר וּבְמִצְנֶ֥פֶת בַּ֖ד יִצְנֹ֑ף בִּגְדֵי־קֹ֣דֶשׁ הֵ֔ם וְרָחַ֥ץ בַּמַּ֛יִם אֶת־בְּשָׂר֖וֹ וּלְבֵשָֽׁם׃

He shall put on the holy linen coat, and he shall have the linen breeches upon his flesh, and shall be girded with a linen girdle, and with the linen mitre shall he be attired: these are holy garments; therefore shall he bathe his flesh in water, and so put them on.