The Torah in Parashat Shemini (Vayikra 10:6) commands the Kohanim, “Rashechem Al Tifra’u” – that they must not let their hair grow long. This establishes a prohibition forbidding the Kohanim from serving in the Bet Ha’mikdash with long hair. The Gemara explains that this refers to letting one’s hair grow for thirty days. This conclusion is reached based on the parallel between the word “Tifra’u” and the related word “Pera” used in reference to the Nazir’s obligation to allow his hair to grow. Just as a Nazir’s status lasts for thirty days unless he stipulates otherwise, the period beyond which a Kohen may not allow his hair to grow before serving in the Bet Ha’mikdash is thirty days. It is uncertain whether we apply the rule of “Miksat Ha’yom Ke’kulo” (“part of the day is regarded as the entire day”) to consider the Kohen’s hair long already on the morning of the thirtieth day, or if it is considered long only after the conclusion of the thirtieth day. The Sefer Ha’hinuch explains that the purpose of this prohibition is “Le’hagdalat Ha’bayit” – to help maintain an aura of awe and grandeur in the Bet Ha’mikdash. The Bet Ha’mikdash is to be a place where people are inspired to repent and to humble themselves before G-d. Therefore, it was vitally important for the Kohanim to create an atmosphere of reverence that would have this kind of impact upon the people. If the Kohanim were to enter appearing disheveled, this would undermine the atmosphere of awe, thus diminishing from the emotional impact that the experience of visiting the Bet Ha’mikdash is meant to have upon the people. Moreover, just as Megilat Ester says that it was forbidden to appear in the royal courtyard wearing sackcloth – the clothing of mourners – all the more so, it is inappropriate to appear in the Bet Ha’mikdash looking like a mourner. The Kohanim are to exude joy and vitality, and if they serve with long hair, they appear like mourners, as though they are unhappy serving G-d. Thus, the Torah commanded the Kohanim not to appear in the Bet Ha’mikdash with long hair. A regular Kohen violates this prohibition only by entering the Bet Ha’mikdash with long hair, whereas the Kohen Gadol transgresses this prohibition by letting his hair grow for thirty days, regardless of where he is. Due to his unique stature of sanctity, the Kohen Gadol may not allow his hair to grow even if he does not enter the Bet Ha’mikdash. Of course, this command is applicable only in the times of the Bet Ha’mikdash, and only to the Kohanim. A Kohen who serves in the Bet Ha’mikdash with long hair is liable to Mita Bi’ydeh Shamayim (death at the hands of G-d, as opposed to execution by the court). A Kohen who enters the Bet Ha’mikdash with long hair but does not perform the Aboda (service) is liable to Malkut. Aboda performed by a Kohen with long hair is not invalidated, even though the Kohen violated the Torah’s command by performing the service in such a state. The Ramban was of the opinion that the Torah prohibition applies only to performing the Aboda with long hair. In his view, simply entering the Bet Ha’mikdash with long hair, without performing any service, is forbidden only Mi’de’rabbanan – by force of Rabbinic enactment. The Sefer Ha’hinuch, however, follows the view of the Rambam, that even just entering the Bet Ha’mikdash with long hair constitutes a Torah violation, albeit one which is punishable by Malkut and not Mita Bi’ydeh Shamayim. The Kohanim were divided into different Mishmarot – rotations, with a different group of Kohanim serving in the Bet Ha’mikdash each week. The policy was that every Kohen would need to take a haircut before beginning his Mishmar (rotation) in the Bet Ha’mikdash. They were not permitted to take haircuts during the week of their Mishmar, in order to ensure that they would not begin their Mishmar appearing disheveled. This resembles the prohibition enacted by the Sages forbidding haircutting during Hol Ha’mo’ed, in order to ensure that one properly gr