Takfir

Takfir () is an Arabic and Islamic term which denotes excommunication from Islam of one Muslim by another, i.e. accusing another Muslim of being an apostate. The word is found neither in the Quran nor in the ḥadīth literature; instead, kufr ("unbelief") and kāfir ("unbeliever") and other terms employing the same triliteral root K-F-R appear.

Since according to the traditional interpretations of Islamic law (sharīʿa) the punishment for apostasy is the death penalty, and potentially a cause of strife and violence within the Muslim community (Ummah), an ill-founded takfir accusation was a major forbidden act (haram) in Islamic jurisprudence, with one hadith declaring that one who wrongly declares a Muslim an unbeliever is himself not an apostate but rather one who has committed a minor shirk. In the history of Islam, a sect originating in the 7th century CE known as the Kharijites carried out takfīr against both Sunnī and Shīʿa Muslims, and became the main source of insurrection against the early caliphates for centuries. Traditionally, the only group authorized to declare another Muslim a kāfir are the scholars of Islam (Ulama), which affirm that all the prescribed legal precautions should be taken before declaring takfīr, and that those who profess the Islamic faith should be exempt.