Ali [radiyallaahu-anhu] said about the Khawaarij:
They are neither Qurraa [i.e. reciters of the Qur’aan who follow it as it should be followed] nor are they a people of astute understanding in the religion, nor are they scholars of Tafseer. By Allaah! If they were to be placed in charge over your affairs, they would [perpetrate] the deeds of Chosroes and Heracles amongst you.
[Taareekh At-Tabari 3/1117]