ABUSIVE LANGUAGE is forbidden by the Muslim law, and the offender must be punished according to the discretion of the Qazi. Abu Hanifah says: “If a person abuse a Musalman by calling him an ass or a hog, punishment is not incurred, because these expressions are in no respect defamatory of the person to whom they are used, it being evident that he is neither an ass nor a hog. But some allege that in our times chastisement is inflicted, since, in the modern acceptation, calling a man an ass or a hog is hold to be abuse. Others, again, allege that it is esteemed only to be abuse when the person of whom it is said occupies a dignified position. According to Abu Hanifah, the greatest number of stripes that can be inflicted for abusive language is thirty-nine. (Hamilton’s Hidayah, vol. ii., 78.)
Muhammad is related to have said “Abusing a Muslim is disobedience to God, and it is infidelity for anyone to join such an one in religious warfare.” (Mishkat, xxii. 2.)

Based on Hughes, Dictionary of Islam