fight, make peace between them. But if one of them transgresses against the other, fight the transgressing group until it returns to Allah’s command. If it returns, reconcile them with justice and act equitably. Surely Allah loves those who act equitably.”
Thus, He did not command fighting the transgressing group at the outset. Initiating fighting is not commanded. Rather, if they fight, He commands reconciliation between them; then, if one group transgresses, it is to be fought. Hence some jurists have said that fighting must not be initiated against rebels until they themselves fight.
As for the Kharijites, the Prophet—may Allah bless him and grant him peace—said concerning them:
“Wherever you encounter them, kill them, for whoever kills them will have a reward with Allah on the Day of Resurrection.”
He also said:
“If I live to encounter them, I will surely kill them as ‘Ād were killed.”
The same applies to those who withhold zakat: al-Siddīq and the Companions initiated fighting against them. Al-Siddīq said:
“By Allah, if they withheld from me even a young female goat that they used to give to the Messenger of Allah—may Allah bless him and grant him peace—I would fight them over it.”
They are to be fought if they refuse to fulfil their obligations, even if they acknowledge that these are obligatory. The jurists then differed over whether someone who withholds both, and whom the ruler fights on that account, is a disbeliever despite acknowledging their obligatory nature. They held two positions, both reported from Ahmad, just as two positions are reported from him concerning whether the Kharijites are disbelievers.
As for those whose offence is rebellion alone, they do not become disbelievers, according to the consensus of the leading religious scholars. The Quran explicitly affirms their faith and brotherhood despite the fighting and transgression. And Allah knows best.