Rather, it has been successively narrated (tawaatara) from him that he commanded fighting against the Khawaarij, the Renegades, those whom the Chief of the Believers, Alee bin Abee Taalib (radiallaahu anhu), fought against at Nahrawaan, after they had revolted against him at Harooraa. For the narrations (sunan) from the Prophet (sallallaahu alaihi wasallam) were in abundance (i.e. spread, known) concerning fighting against them (the Khawaarij), and when Alee (radiyallaahu anhu) fought against them, he rejoiced with fighting against them, and he also narrated the hadeeth concerning them, and the Companions also agreed upon fighting them (7).
And similarly the people of knowledge after them, this fighting (against the Khawaarij) was not like the fighting of the people of the Camel and Siffeen and other than them, from those matters in which no text or Ijmaa' has come, and neither any praise of the noble ones who entered into it. Rather, they were remorseful about it, and also returned (i.e. recanted) from it.
And this (aforementioned) hadeeth (i.e. concerning al-Hasan) is from the signs of the Prophethood of our Prophet Muhammad (sallallaahu alaihi wasallam), when he mentioned about al-Hasan whatever he mentioned, and praised him for what he praised him. So whatever he mentioned and whatever he praised was in agreement with the truth that actually occurred after more than 30 years...
And this very thing is the actual wisdom that the legislator (sallallaahu alaihi wasallam) was attempting to bring about and nurture in his prohibition of revolting against the rulers, and he taught abandonment of fighting in times of fitnah - even if those who fell into this considered that their intent (desire) was to enjoin the good and forbid the evil.
And it is actually from this angle (i.e. intending to enjoin good and forbid evil) that the Khawaarij made lawful the (raising of the) sword against the people of the qiblah, until they killed Alee and others from the Muslims. And similarly, those who agreed with them in revolting against the rulers, with the sword, in general terms - such as the Mu'tazilah, the Zaydiyyah, and the Fuqahaa (Jurists), and others. Such as those who revolted alongside Muhammad bin Abdullaah bin Abdullaah bin Hasan bin Husayn, and his brother, Ibraaheem bin Abdullaah bin Hasan bin Husayn and others (8).