A term often used by Sufis is found also in most of the major languages of the Islamic peoples. It is adab, which means at once comportment, courtesy, culture, refined speech, literature, correct ethical attitudes, and many other concepts. It is really untranslatable and perhaps should be used in English in its Arabic form like terms such as karma and guru, which have entered English recently from Sanskrit, or jihad from Arabic. All traditional societies have tried to inculcate their own forms of adab within members of society from childhood, and Islamic civilization is no exception. For traditional Muslims, adab encompasses nearly all aspects of life from greeting people to eating to sitting in a gathering to entering a place of worship. As for quintessential adab, it has always been associated by Sufis with the actions and words of the Prophet himself. Adab is the means of controlling the passions, which affect and often originate human actions. It is also a way of formalizing human actions in such a way that they display harmony and beauty rather than disorderliness and ugliness.
— Seyyed Hossein Nasr, The Garden of Truth