Parshas Emor commences with a presentation of halachos that would appear to be exclusive to Kohanim:

And Hashem said unto Moshe - Speak unto the Kohanim and say to them: One may not become defiled by the dead, with the exception of a close relative: one's mother, father, son, daughter... They (the Kohanim) may not bald their heads, and the corner of their beard may they not shave, and they may not slash into their flesh. They shall be holy for their God, and not defile the Name of their God, for they bring the offerings of Hashem and shall be holy. A woman who is a zonah and a chalalah shall he (a Kohen) not marry, as well as a divorcee shall he not marry, for he is holy unto his God... (Vayikra 21:1-7) 

Unlike other regulations pertaining to Kohanim, which are of a functional character (such as the many laws of Kohanim offering korbonos), the above regulations reflect the concept of Kedushas Kehunah, the sanctity of the Kohanim's priestly status, and hence relate to the Kohanim's unique spiritual distinction, which must be protected from defilement and treated with respect.

Chazal explain that the middle section of the above opening passages of Parshas Emor, featuring the prohibitions of slashing one's flesh ("s'reitah") and balding one's body ("korchah") in anguish, as well as shaving one's face with a razor, apply to all Jews, as we see elsewhere in the Torah, but that the Torah phrased these three prohibitions here with certain nuances in order to provide added contours to these general prohibitions. (For example, the Torah utilizes the specific words "lo y'galechu" here regarding shaving, so as to prohibit only the use of blades and to permit the use of tweezers and the like; v. Rashi on pasuk 6, from Gem. Makkos 20a.) The obvious question that arises is why the Torah features these three general prohibitions, albeit with added contours, in the middle of a text dealing with the rules of Kohanim. If these three prohibitions apply to all Jews and are not unique to Kohanim, why do these prohibitions appear together with halachos pertaining only to Kohanim?

The Rambam (Hil. Avodas Kochavim 12:7) writes: "The manner of the priests of idolatry was to destroy their beards. Therefore did the Torah prohibit to destroy the beard." Similarly, Sefer Ha-Chinuch (m. 467-468) writes that the prohibitions of s'reitah and korchah reflect practices common to idolaters. Hence, by slashing one's flesh, balding one's body and destroying one's beard, a person places the emblems of avodah zarah (idolatry) upon his anatomy.

We can now explain why these three prohibitions, even though they pertain to all Jews, appear in the Torah’s treatment of Kohanim as people elevated to Hashem’s special service as manifest through Kedushas Kehunah. For just as a Kohen may not engage in that which compromises his Kedushas Kehunah, even while not performing Avodah (Mikdash service), so too must he not defile his body with idolatrous features. The body of one who is a priest of Hashem, even while not in active service, cannot bear imagery which the Rambam describes as that of “the manner of the priests of idolatry”, and other signs of avodah zarah. Such is a desecration, for one cannot be ennobled to the priesthood of Hashem while bearing symbols of devotion to idols. This is precisely why the Torah presents the prohibitions of s'reitah, korchah and destroying one's beard in the midst of presenting the special rules of Kedushas Kehunah, as these prohibitions are of special and unique significance when it comes to Kohanim, even though these prohibitions apply to all Jews.

Taking a step back, we are taught a clear and broad message that speaks to us all, even if we are not Kohanim. The Torah is concerned not only with one's commitments and affiliations while davening, learning Torah or performing other mitzvos. Rather, since every Jew is part of the Am Ha-Nivchar, the nation chosen by Hashem to be close to Him and to represent His Will among humanity, it is necessary for our identities to at all times be associated with Hashem and not with that which is inconsistent with His mandate. To be a frum Jew in shul and to act otherwise elsewhere, or to present an image of seriousness about Avodas Hashem only when engaged in a mitzvah, is not acceptable. A Jew must always bear the badge of dignity and holiness as a member of Hashem’s nation, under all circumstances, just as Kohanim must exhibit an image of Divine Service, even while not in performance thereof. This is the unique and powerful message of Parshas Emor for us all.