LEV92 Kohanim shall not enter the Sanctuary if the hair on their heads has grown long and wild. Key concept: To preserve and promote the atmosphere of glory and majesty in the Beis HaMikdash, in any way possible. To this end, the Kohanim serving there are forbidden to enter there displaying an appearance that resembles that of a mourner or other aggrieved people. Rather, their appearance and demeanor must indicate joy, happiness and pleasure. This mitzvah falls in line with the guiding principle stated above--that all matters of the Beis HaMikdash are to inspire us to think and act with virtue, so that we distance ourselves from all that is ugly, crass and sinful. Accordingly, Kohanim who enter the Beis HaMikdash cannot exhibit any reminder of death, sadness or grief. Proper service of Hashem is with joy, so the Kohanim must have a happy, dignified appearance while performing their duties. Thereby, all who come to the Beis HaMikdash are impressed by the atmosphere of blessing, splendor, majesty, and holiness. Awe enters their hearts and they are inspired to seek such greatness and holiness for themselves. Thereby they become fit for Heaven's blessings.