The Seven Day Isolation Period for the Kohen Gadol Prior to Yom Kippur
The opening mishna in Yoma describes how the Kohen Gadol was isolated for seven days prior to Yom Kippur in a designated gallery located in the vicinity of the Beit Ha-Mikdash.
The gemara cites a machloket between R. Yochanan and Reish Lakish as to the source of this practice. R. Yochanan derives this isolation from the seven day isolation period known as Milu’im prior to the inauguration of the Mishkan (as described in the end of Parashat Tzav). Just as the Kohanim spent seven days posted in the Mishkan, the Kohen Gadol should similarly be “posted” in the Mikdash seven days before Yom Kippur. Reish Lakish cites a different source – Moshe's seven-day period atop Har Sinai prior to receiving the Torah. Moshe was actually isolated for only six days, but the Kohen Gadol must add a day to account for possible nida-tuma complications.
It appears obvious that the SOURCE of this sequestering impacts its NATURE and FUNCTION. Moshe isolated himself in preparation for encountering the Shekhina at Har Sinai. Reish Lakish views the period pre Yom Kippur as facilitating a similar encounter when the Kohen Gadol enters the Kodesh Ha-Kodoshim on Yom Kippur. In fact, the Ran (Derashot Ha-Ran, 4th derasha) makes this association. The seven day period modeled after the preparation for Har Sinai is necessary to prepare for encountering the Shekhina on Yom Kippur.
In contrast, R. Yochanan compared the pre-Yom Kippur sequestering to the Milu’im period and evidently viewed it as a preparation necessary for AVODA ceremonies in the Mikdash. Just as the first historical avoda in the Mishkan required orientation through preparation and isolation, similarly the Yom Kippur service (which effectively refreshes the Mishkan by cleansing it of its accumulated impurity) requires an isolation period.
The debate about the source would also see to influence the SCOPE of this rule. A parallel mishna in Para speaks of a similar seven day period for the Kohen who processes the para aduma. According to R. Yochanan, it is POSSIBLE that this practice of isolation prior to para aduma stems from the same source as the pre-Yom Kippur isolation practice. Just as preparation for the special Yom Kippur avoda requires seven days of isolation, the unique avoda surrounding the para aduma similarly requires seven days of isolation. In fact, R. Yochanan derives each of these similar practices from the pasuk about the Milu’im. Though ultimately, the gemara (3b) concludes that this statement is a reflection not of R. Yochanan's personal opinion, but of his teacher. R. Yochanan's source certainly ALLOWS twinning the para aduma isolation with the Yom Kippur isolation and allows deriving them from the same pasuk. In contrast, Reish Lakish's source – Har Sinai – has little relevance to para aduma, which is processed OUTSIDE the precincts of the Mikdash – and it is unrelated to the encounter with the Shekhina. Evidently, Reish Lakish would subscribe to the opinion that the pre-Para Aduma isolation IS NOT de-oraita but only Rabbinic. In fact, the gemara in Yoma (3b) cites several opinions which claimed that the isolation period prior to para aduma is only a ma'ala (a safeguard) – typically suggestive of a Rabbinic-based halakha.
Alternatively, Reish Lakish's model may apply to ANY encounter with the Shekhina, even if not rooted in any avoda ceremony. A very famous position of the Vilna Gaon suggests that the Kohen Gadol could enter the inner sanctum as often as he wished, even if it were not Yom Kippur. R. Menachem Zemba (in his Chiddushim, siman 13) asserted that if the isolation period stems from the encounter with the Shekhina, it would be required even in non-Yom Kippur visits. Obviously, R. Yochanan's model would be irrelevant to a random entry that does not incorporate any avoda.
It appears that the gemara recognized this difference between R. Yochanan and Reish Lakish. Immediately upon listing R. Yochanan's opinion, the gemara questions his application SPECIFICALLY to Yom Kippur. Perhaps other special days in the Mikdash which require special avoda ceremonies ALSO require a prior seven day separation period. The gemara succeeds in deflecting all these questions and concludes that ONLY Yom Kippur requires this preparation. Fundamentally, however, the gemara assumes that R. Yochanan should not discriminate between Yom Kippur and any other special day with its special avoda. Interestingly, this line of questioning is not posed to Reish Lakish. By citing the Sinai experience as the model for separation, Reish Lakish was obviously tethering the practice to an eventual encounter with the Shekhina. This encounter occurs only on Yom Kippur and NOT on other special festival days. Hence, it is illogical to suggest applying this practice to those days.
This question as to whether the period prepares for unique avoda or for encounter with the Shekhina may influence the question of WHERE the Kohen Gadol resided during this period. The mishna assigns the Parhedrin gallery, which was located on the northern flank of the Mikdash as his seven day retreat. Was this gallery considered part of the actual halakhic Mikdash? Is it necessary for the Kohen Gadol to reside in the actual Mikdash? Tosafot (2a) cite two different opinions, but from the Rambam's comments (Avodat Yom Ha-Kippurim 1:3) it is apparent that this gallery was incorporated within the Mikdash.
A different comment of Tosafot (8a) also appears to cite two opinions about the location of the Palhedrin gallery. In their second approach, which is clearly committed to the fact that this gallery was located within the confines of the Mikdash, Tosafot deals with an apparent contradiction. Typically, EVEN SITTING is not allowed in the Mikdash precincts. How, then, can the Kohen Gadol SLEEP there? Tosafot maneuver their way out of this jam by suggesting that the gallery’s doors opened outward, emptying them from halakhic kedusha and enabling sitting and even sleeping in them. However, as they WERE built in Mikdash SPACE, they are still considered PART of Mikdash. In their second approach, Tosafot are so committed to positioning the Kohen Gadol in the Mikdash that they must creatively solve the problem of the halakhic prohibition.
Clearly, R. Yochanan's version of the sequestering would mandate presence IN THE MIKDASH. Since the period helps prepare for the avoda which occurs in the Mikdash, the Kohen should be stationed there. After all, the template for this period is the Milu’im week, during which the Kohen was posted in the Mikdash. Reish Lakish's model of preparing to encounter the Shekhina would not require the Kohen Gadol's presence in the Mikdash, much like Moshe did not prepare for his encounter with the Shekhina by residing in Mikdash precincts .
An additional question surrounds the schedule during this week. Must the Kohen Gadol remain full time in the gallery, or may he take brief home visits? The Tosafot Yeshanim (Yoma 6a, s.v. mi-beito) claims that he CAN leave for short periods, while a contrasting Tosafot Yeshanim (Yoma 10b) claims that he must remain fully sequestered. Again, if the model for this period is the Milu’im, he may be required to remain full time, as the earliest kohanim did. However, if the model is Moshe's seven day period atop Har Sinai, perhaps his preparation would not be disturbed by short visits home.
R. Soloveitchik suggested an interesting question regarding the Kohen Gadol’s practicing the avoda during this week. The gemara (4a) claims that during this entire week, two experts instructed the Kohen Gadol. This parallels how Moshe instructed Aharon during the Milu’im ceremony. Is this instruction ABSOLUTELY necessary? If the Kohen Gadol were himself an expert, would he still require instruction? Again, according to R. Yochanan's model, perhaps this instruction is integral. Just as the seven day Milu’im period enabled instruction, this seven day period should similarly facilitate the process. However, Reish Lakish's model of separation would not require instruction unless it were technically necessary to train an inexperienced Kohen Gadol.