Broadly, takfir is the Muslim term for excommunicating, or declaring apostate, a Muslim whose acts are in violation of the faith. Mainstream Sunni Islam generally avoids this other than in extreme cases, given the principles that it is bad to spread fitna (dissension) among believers, and, for man to declare takfir is to make a judgment properly that of Allah.
There are, even within Sunni theory, cases where a legal definition of apostasy exists, such as the formal renunciation of the religion by a Muslim. In general, however, even well-qualified clerics are reluctant to make such a declaration.
Within Salafism and its offshoots, however, the concept is much more important. Muhammad Ibn 'Abd al-Wahhab, the founder of Wahhabism in the 19th century, cited Ibn Tamiyya as justification for declaration of takfir. Wahhab specifically considered Sufism and other religious innovation (bid'a) as takfir.
In modern usage, takfiri tends to refer to the practices of offshoots of the Muslim Brotherhood. One such group was, Takfir wal-Hijra (TwH, Excommunication and Holy Flight/Emigration), was established Shukri Mustafa in 1971. Their ideas merged with those of Sayyid Qutb in affecting more recent extremists, such as Ayman al-Zawahiri.
Not all Islamists practice takfiri. After the 2008 Mumbai attacks, Hizbollah's chief of international relations, Sayyid Nawwaf al-Musawi, Hizbollah’s international relations head, called the Mumbai attackers takfiris, and said they were opposed to “Takfiri ideas which makes others targets of killing and aggression...We said that the deadly Takfiri thought has been tearing apart the body of the Muslim community, inflicted massacres on them and shedding much of their blood.” Al-Musawi contrasted them to “genuine Islamic principles [that] consider others either brothers in religion or partners in God’s creation, affiliated to the same human race.”Jordanian King Abdullah II, has criticized extreme takfir, but there is a takfiri faction within Jordan's salafists. Speaking on behalf of the King, Prince Ghazi, personal envoy and special adviser to the King, spoke to the 17th annual Islamic Fiqh Academy Conference, and said the first priority for them was addressing disunity. "Without this, it would be unreasonable to call for the solidarity and cooperation of Muslims, countries and peoples, on the basis that we are one nation,” The King's speech called for Muslim scholars, attending from 43 countries to fight takfiri ideology, and resist fatwas issued by those not qualified to do so.
If there are those among us who declare the adherents of any madhahib an apostate, or who dare to issue fatwas without being qualified or who do not respect the sanctity of Muslim blood, honour and property, then there should be those who stand up to all these matters that fracture the nation and abuse our faith.
A letter, distributed on the Internet by a newly formed group in the town of Zarqa, with signatories including Loqman Reyalat, Jarrah Qaddah, Abu Soraqa and Abu Muhammad al-Maqdisi, called Awqaf imams, appointed by Jordan's Ministry of Awqaf Islamic Affairs and Holy Places, kafirs” (infidels). “One of them proudly announced that he has not prayed after any of those [sic] imams in the last five years, another one said that he has not in the last ten.” Some consider the appointed imams to be government employees, and brand all government employees as kafir.
- Trevor Stanley (July-December 2005), Definition: Kufr - Kafir - Takfir - Takfiri, Perspectives on World History and Current Events
- Atul Aneja (December 6, 2008), "Hizbollah suspects Takfiri extremists", The Hindu
- Mahmoud Al Abed (June 25, 2006), "King urges Muslim scholars to fight takfiri ideology, fatwas", Jordan Times
- Murad Batal Al-shishani (November 19, 2008), "The Neo-Zarqawists: Divisions Emerge between Jordan’s Salafist Militants", Terrorism Focus, Jamestown Foundation