Is declaring a Companion—like Ali ibn Abi Talib—to be a disbeliever considered apostasy, or is the one who does so not considered an apostate, as is the case with the Kharijites?

First: Whoever declares the majority or generality of the Companions to be disbelievers is himself a disbeliever, for he denies revelation and rejects what is known by necessity to be part of the religion. The implication of his statement is that the transmitters of the Qur’an and Sunnah (definition) are disbelievers or transgressors, and that this Ummah is the worst of nations.

Second: Whoever declares a single Companion to be a disbeliever: 1. If his disbelief or cursing is due to their Companionship, then he is a disbeliever. 2. If his disbelief is not due to their Companionship, and the Companion is one whose virtue has been established by texts, such as Abu Bakr, Umar, Uthman, Ali, and Aisha, then there is a difference of opinion, and a group has deemed him a disbeliever.

Third: The Khawarij declared Ali, Muawiya, and those Companions who accepted the arbitration to be disbelievers. The majority view is that they are transgressors, not disbelievers. This is either because declaring an individual Companion to be a disbeliever is not considered disbelief by some, or because they (the Khawarij) were misinterpreting (the texts). The hadiths reported concerning them do not indicate their specific disbelief, but rather are texts of warning to show the enormity of their crime, and evidence of their misguidance, innovation, and deviation.