A kohen who has a physical blemish is unfit for the avodah, the service in the Bais Hamikdash. The question begs itself, why? Is it the kohen's fault that he has a defect? Is it not enough that he suffers from the constant discomfort presented by this defect that he is also shunned from the kedusha - holiness, of the Bais Hamikdash? Certainly, there is no more humble, submissive person than one who is deformed. Wouldn't he be especially suited for the service? Why must he keep his distance?

     Answers R' Avigdor Miller zt”l, all these factors are true, but, alas, "A person sees with his eyes." If those who come to the Bais Hamikdash see a deformed kohen, the sanctity of the avodah would be undermined in their eyes, causing a Chilul Hashem - desecration of Hashem's name. As much as we may not realize it, appearances are very important and even a kohen has to look his best when doing his priestly duties.

     So too, each religious Jew serves, in the eyes of his secular onlookers, as a representative of the Jewish religion. This is all the more true with regard to yeshiva students, and those who hold public, religious positions. If such a person appears with unkempt attire, if he speaks abruptly and ignores conventional guidelines of etiquette and courtesy, he may very well cause a Chilul Hashem, a sin for which there is no atonement. On the other hand, if his behavior is proper, his appearance tidy and pleasant, the posuk says, "Yisroel, in whom I  am glorified." Such behavior brings about a Kiddush Hashem, a mitzvah loftier than any other.