Abu Muḥammad Ibn Ḥazm reports a consensus that trimming the mustache and letting the beard grow is a religious obligation. He cited as proof the hadith of Ibn ʿUmar: “Differ from the polytheists: shorten the mustaches and allow the beards to grow,” as well as the marfūʿ hadith of Zayd ibn Arqam: “Whoever does not trim his mustache is not one of us,” which al-Tirmidhī judged sound, along with other evidences. Ibn Mufliḥ states in al-Furūʿ: “According to our scholars, this wording indicates prohibition,” and he writes in al-Iqnāʿ: “Shaving it is forbidden.”

Al-Ṭabarānī transmits, on the authority of Ibn ʿAbbās, that the Prophet ﷺ said: “Whoever mutilates the hair has no share with Allah.” Al-Zamakhsharī explained: “This means transforming it into a disfigurement by plucking it, shaving it from the cheeks, or darkening it with black dye.” Ibn al-Athīr adds in al-Nihāyah: “Mutilating the hair refers to shaving it from the cheeks; it is also said that it means plucking it or coloring it black.”

Imām Aḥmad likewise relates—through Abū Hurayrah—that the Messenger of Allah ﷺ said: “Let the beards grow and trim the mustaches; do not imitate the Jews and Christians.” Al-Bazzār records a marfūʿ report from Ibn ʿAbbās: “Do not imitate the non-Arabs; let the beards grow.” And Abū Dāwūd transmits from Ibn ʿUmar that the Messenger of Allah—peace and blessings be upon him—said: