Almost everything known about the Kharijites comes from people who opposed them. The chronicles that describe their revolts, their doctrines and their downfall were written by the very caliphates that crushed them, generation after generation of hostile transmission standing between a modern reader and whatever the Kharijites actually believed about themselves.
Poetry is the one exception. Kharijite leaders and fighters composed verse, and much of it survived, copied down inside the same hostile historical tradition but never fully absorbed into its argument, because a poem resists paraphrase in a way a chronicle does not. The historian Hannah-Lena Hagemann has called it the only genuinely Kharijite material available today. Its themes are consistent across many hands: piety pushed to the point of self-sacrifice, the conviction that armed rebellion, khuruj, against an unjust ruler is not merely permitted but owed to God, and an unflinching readiness for martyrdom.
No voice in that body of verse looms larger than Imran ibn Hittan, called the greatest Kharijite poet by the Arabist Michael Cooperson. Ibn Hittan wrote in praise of Abu Bilal, a Kharijite leader whose death only sharpened his own commitment to revolt, and, in lines that scandalized later generations, praised Ibn Muljam, the man who killed the caliph Ali. Sermons and poems by leaders like him were gathered during and after the Kharijite period into collections called diwans.
Centuries later, the modern scholar Ihsan Abbas gathered what survives of this poetry into a single volume, first published in 1974 and reissued in an expanded fourth edition in 1982 as Diwan Shi'r al-Khawarij. Library catalogs the world over shelve it under a subject heading that states plainly what it is: Kharijites in Arabic poetry. It is not a history written about the Kharijites by their enemies. It is the closest thing that survives to the Kharijites speaking for themselves.