The chapter
Ali accepted the pledge over a city still bloody from Uthman's murder, and spent five years proving that the hardest arena of knowledge is not the lecture but the storm. The Qur'an had legislated for exactly his years in advance: "if two parties of the believers fight, make peace between them" (49:9), and its next verse kept both camps inside the faith: "the believers are but brothers." Ahl al-Sunnah read the era through those verses, and through the Prophet's ﷺ words about the players: Ammar, "killed by the transgressing party"; al-Hasan, the sayyid through whom Allah would reconcile two great parties; and the Khawarij, foretold with an archer's precision, "they pass through the religion as the arrow passes through the prey" (Bukhari 6930), reciting a Qur'an that does not pass their throats.
The Camel ended with Ali escorting the Mother of the Believers home with full honor, her regret and his reverence both on the record. Siffin bled into arbitration; the arbitration bred the Khawarij, who declared every sinner an infidel and made takfir a weapon; at Nahrawan he broke them, and he taught the ummah forever how to classify such people: do not call them disbelievers, he said, from disbelief they fled; they are brothers who transgressed against us. His capital in Kufa ran on a judge's temperament: the caliph appearing before his own qadi against a Jewish defendant over a coat of mail, and losing the case for lack of evidence, and the defendant embracing Islam at the sight.
In Ramadan of 40 AH, the Khariji Ibn Muljam struck him with a poisoned blade at Fajr. His last commands banned mutilation and collective revenge: a life for a life, nothing more. The Codex closes the four with the adab the ummah's imams fixed: love them all, ask mercy for all who fought, and hold the tongue where the swords once were, "that is a nation that has passed; theirs is what they earned" (2:134). What remains for us is what Ali carried through the storm: that knowledge, justice, and restraint are one discipline, and it is hardest, and most needed, when believers are the ones at odds.