Reference for Yoma 63:1

עשרה קידושין אלא לרבנן תשעה הוו אמרי לך רבנן קידושא בתרא כי פשיט בגדי קדש ולביש בגדי חול עביד ליה התם

ten sanctifications, but according to the Rabbis, they are only nine? - The Rabbis will answer you: The last sanctification is made when he strips off the holy garments and puts on the profane<span class="x" onmousemove="('comment',' At the end of the service of the Day of Atonement, as he strips off' the holy garments to don profane ones.');">¹</span> ones. Our Rabbis taught: And Aaron shall come into the tent of meeting<span class="x" onmousemove="('comment',' Lev. XVI, 23.');">²</span>

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