St. Cyril of Jerusalem: Believe the Resurrection
4 hours ago
The simple reason why Orthodox priests wear beards is because, as a Nazarene, Our Lord had a beard, as can be seen from any icon. Since the priest is a dispenser of sacramental grace and an icon of Christ, he should physically resemble Our Lord, not only in wearing a robe or cassock (which need not at all be black, contrary to popular myth), but also in being bearded and having the same hairstyle (long hair with a parting down the middle). Taken from here.
Sometimes this is not possible, especially if the priest has to do a secular job (and also if the priest's wife objects to long hair and untrimmed beard!)
...by the 11th Century that it was listed among the reasons for the Anathema pronounced by Cardinal Humbert on July 15, 1054 against Patriarch Michael in Constantinople which precipitated the Western Church's final falling away from the Orthodox Church: "While wearing beards and long hair you [Eastern Orthodox] reject the bond of brotherhood with the Roman clergy, since they shave and cut their hair." Taken from here
Those too incur the excommunication of this Canon, according to Zonaras, who do not put a razor to their head at all, nor cut the hair of their head, but let it grow long enough to reach to the belt like that of women, and those who bleach their hair so as to make it blond or golden, or who twist it up and tie it on spills in order to make it curly; or who put wigs or rats on their head. This excommunication is incurred also by those who shave off their beard in order to make their face smooth and handsome after such treatment, and not to have it curly, or in order to appear at all times like beardless young men; and those who singe the hair of their beard with a redhot tile so as to remove any that is longer than the rest, or more crooked; or who use tweezers to pluck out the superfluous hairs on their face, in order to become tender and appear handsome; or who dye their beard, in order not to appear to be old men.