In this video, Shaykh Dr. Yasir Qadhi unravels details about the Kharijite group, their interactions & tensions with Ali Ibn Abi Talib RA and the statements made by the Prophet Muhammad ﷺ regarding this particular group of people.
The Messenger of Allah said: They kill the Muslims and spare the idolaters. If I live to see them I will kill them like the killing of (the people of ‘Aad). [Bukhari and Muslim]
Ibn Taymiyyah writes:
The Kharijite sect was the first to declare Muslims to be unbelievers because of their sins. They charged as unbelievers whoever disagreed with their innovations and they made lawful the spilling of blood and the taking of wealth. This is the condition of the people of innovation, that they invent some religious innovation and then they excommunicate whoever disagrees with them concerning it. Rather, the people of the Sunnah and the community follow the Book and the Sunnah and they obey Allah and His Messenger and follow the truth. They have mercy upon the creation.
Source: Majmū’ al-Fatāwá 1/278
The Khawarij revolted against the authority of Ali RA after he agreed to arbitration with Muawiyah I, to decide the succession to the Khilafat following the Battle of Siffin. The Khawarij opposed arbitration as a means to choose a new ruler on the grounds that "judgement belongs to Allah alone". They considered arbitration a means for people to make decision while the victorious was determined by Allah. A Khariji later assassinated Ali RA.
More facts about them are divulged in the talk. Please do listen intently.