Kharijites

The Kharijites were an early Islamic movement that rejected arbitration after the Battle of Siffin and opposed Ali ibn Abi Talib. They developed distinctive views on legitimate leadership, faith, and grave sin.

Battle of Siffin: A 657 battle between forces loyal to Ali ibn Abi Talib and Muawiya ibn Abi Sufyan. The proposed arbitration after this battle triggered the Kharijite break with Ali.
Quran: The central scripture of Islam, understood by Muslims as the word of God revealed to Muhammad. Kharijite appeals to divine judgment drew on Quranic language and authority.
Tahkim: The use of human arbitration to settle a dispute, especially the arbitration following the Battle of Siffin. Rejecting tahkim became the movement's defining break with Ali.
Sunni Islam: The largest branch of Islam, whose traditions recognize the first four caliphs as rightly guided leaders. Sunni accounts of communal authority differ from Kharijite demands for a ruler's strict righteousness.
First Fitna: The first major civil war among Muslims, fought from 656 to 661 over political and religious authority. The Kharijites formed amid this conflict over who could lead the Muslim community.
Caliphate: The institution of political and religious leadership over the Muslim community after Muhammad's death. Kharijite debates centered on who could legitimately hold this authority.
Major sin in Islam: A grave violation of Islamic law or moral duty, whose effect on a Muslim's faith has been debated by theologians. Kharijite doctrines connected grave sin with a person's standing in the community.
Shia Islam: The branch of Islam that holds Ali and his descendants had a special claim to leadership of the Muslim community. Shia legitimacy rests on Ali's authority, whom Kharijites rejected after the arbitration.
Ali ibn Abi Talib: The fourth Sunni caliph and first Shi'a imam, who ruled from 656 until his assassination in 661. Kharijites first emerged as supporters of Ali before rejecting his acceptance of arbitration.
Imamate: The doctrine and institution of leadership in the Muslim community, understood differently across Islamic traditions. Kharijites developed a distinctive account of the qualifications for communal leadership.

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