Yoma 71A

שכל הפרשה כולה נאמרה על הסדר, חוץ מפסוק זה.

as the whole portion of the service of the day detailed in Leviticus is written in this order, and the service must be performed in that order, except for this verse, which is stated out of order and is performed only later. The verse detailing his reentry (Leviticus 16:23) is written before the verse detailing the sacrifice of the rams (Leviticus 16:24), but in fact the reentry occurs only after the sacrifice of the rams.

מאי טעמא? אמר רב חסדא: גמירי, חמש טבילות ועשרה קידושין טובל כהן גדול ומקדש בו ביום,

The Talmud asks: What is the reason to assume this verse is written out of order? Rav Ḥisda said: They learned as a tradition that the High Priest performs 5 immersions and 10 sanctifications of his hands and feet when he changes clothing on that day. Each time the High Priest changes between the white and golden garments, he sanctifies his hands and feet, immerses, dresses in the new set of garments and then once again sanctifies his hands and feet.

ואי אמרת כסדרן כתיבי, לא משכחת לה אלא שלש טבילות וששה קידושין.

And if you say that the verses, including this one, are written in order, you find only 3 immersions and 6 sanctifications. Read in order, the verses indicate only 3 changes of garments, which involve 3 immersions and 6 sanctifications. In order to arrive at the requisite numbers of 5 immersions and 10 sanctifications one must assume that the High Priest’s reentry into the Holy of Holies takes place at a later time, after he has already changed into the golden garments. This would require him to change into the white garments and then back into the golden garments, providing an additional two immersions and 4 sanctifications.