- לשכת בית האבן
The opening Mishnah states, שבעת ימים קודם יום הכפורים מפרישין כהן גדול מביתו ללשכת פרהדרין – Seven days before Yom Kippur they sequester the Kohen Gadol from his house, to the Parhedrin Chamber. The Gemara brings another case in which a Kohen is sequestered, citing a Mishnah from Parah that states that seven days before the burning of the parah adumah they would sequester the Kohen who was to burn the parah from his house, to the chamber in front of the Birah, in the northeast of the Temple courtyard, ולשכת בית האבן היתה נקראת – and it was called “The Chamber of the Stone House.” It was called the לשכת בית האבן because all the procedures for the parah were performed with keilim made of dung, stone or clay. The Gemara explains that because a tevul yom is valid for performing the avodah of the parah adumah, they would purposely render the Kohen tamei and immerse him in a mikvah, להוציא מלבן של צדוקין - to negate the views of the Tzadukim who held that the Kohen had to experience nightfall and be completely tahor. The Rabbanon therefore instituted using keilim made of dung, stone or clay that are not mekabel tumah כי היכי דלא ליזלזלו בה – - in order that they do not treat the parah adumah lightly.
- לכפר לעשות
The Gemara asks what the source is that both the Kohen Gadol before Yom Kippur, and the Kohen performing the avodah of the parah adumah, are sequestered for seven days prior to their services, and answers with a statement made in the name of Rebbe Yochanan. The passuk states in the parshah of the miluim, the installation of Aharon and his sons, כאשר עשה ביום הזה צוה לעשות לכפר עליכם – As he did on this day, so Hashem commanded to do to atone for you. "לעשות" אלו מעשה פרה – “To do” – this refers to the avodah of the parah, "לכפר" אלו מעשי יום הכפורים – "To atone" – this refers to the avodah of Yom Kippur. For these services too, the Kohen Gadol must be sequestered.
The Gemara asks that while it is understandable that the entire passuk cannot be referring to the parah, since it does not provide kaparah, why not say the entire passuk is referring to Yom Kippur? It answers that we learn from a gezeirah shavah using the words tzivah, tzivah. It is written here, צוה ה' לעשות and it is written in the parshah of the parah adumah, זאת חקת התורה אשר צוה ה' לאמר – This is the law of the Torah that Hashem commanded saying. Just as for the miluim, the perishah is required, so too by the parah adumah, perishah is required.
- פרישת שבעה ליום אחד
The Gemara challenges Rebbe Yochanan’s interpretation that לכפר refers to the avodah of Yom Kippur and suggests that it could refer to the kaparah gained by other korbanos. After some analysis, the Gemara answers דנין פרישת שבעה ליום אחד מפרישת שבעה ליום אחד – We derive seven days of perishah for a one-day service, (referring to Yom Kippur), from a perishah of seven days for a one-day service, (referring to the eighth day of the inauguration). The Gemara brings two answers why the passuk is not referring to Shemini Atzeres, which could also a case of perishah of seven days for a one-day service.
