Shaving the beard is not permissible, according to the saying of the Prophet Salallaahu alayhi wasallam in an authentic Hadith:
"Clip your moustaches and grow your beards, differ from the polytheists." (Al-Bukhari no.5892 and Muslim no.259)
and his words:
"Pare your moustaches and leave your beards, differ from the Zoroastrians." (Muslim no.260)
The beard is what grows on the cheeks and on the chin, as defined by the author of Al-Lisan and Al-Qamus. It is obligatory to leave the hair which grows on the cheeks and chin and not to shave it or cut it. May Allaah correct the situation of all the Muslims.
Lisanul-'Arab and Al-Qamus al-Muhit: Two famous Arabic dictionaries.