The name khariji (pl. khawarij) has been held to mean, "seceder" or "deserter." They are those who have "gone out against" (kharaja 'ala) Ali, or "went out" and "made a secession" from the camp of Ali in the sense of rebelling against him. Ali's decision to submit the fate of the battle of Siffin to Arbitration did not meet with the approval of his Iraqian soldiers, and about 12,000 of whom deserted and rebelled against him on the march back to Kufa, known as the Kharijis. They also came to be known as Harurites from the place where they were first encamped. Ali referred to them as al-mariqun (those who missed the truth of religion).
Seething with unrest, the Kharijis encamped at Harura, taking as their watch-word la hukma illa lillahi (The decision of God, the word of God alone), a phrase which, ever since it was first coined, has become a favourite with public agitators. The original separatists had three great leaders, namely Shabath bin Ribi al-Riahi, Abdullah bin Kauwa al-Yeshkuri and Yazid bin Qais al-Arhabi from the three principal tribes of Banu Tamim, Banu Bakr and Banu Hamdan. Anxious to prevent another outbreak of fighting, Ali deputed his cousin Ibn Abbas to negotiate a compromise. The Kharijis insisted that Ali should march forthwith against Muawiya, a demand with which Ali could not possibly comply, as he had given his word to abide by the decision of the arbitration. Months later, when Ali having been deposed off by the umpires of arbitration, he sought to raise an army against Muawiya, and expected the Kharijis to flock to his standard, but they made no attempt to join him. Repeated attempts on Ali's part to urge the Kharijis to join him met with total failure. Instead they decided to raise their own independent standard and went into camp at Naharwan, under the leadership of Abdullah bin Wahab al-Rasibi.
Naharwan was a township, situated on a canal of the same name, a few miles east of the Tigris near Madain and between Baghdad and Wasit. Here the Kharijis made extensive preparations for war. Meanwhile, Ali had managed to muster an army for a renewed campaign against Muawiya, and while he was on his way to Syria, a news of the latest outrages by the Khariji fanatics reached him. They had murdered Abdullah bin Khabbab, cutting him down in cold-blood, alongwith his wife and children. Three women of the Banu Taiy had also been put to death in a similarly cruel manner. Pregnant women had been ripped up with the sword, and the aged and impaired cruelly tortured to death.
Ali decided to relinquish Syria for a while and to take field against the yoke of the Kharijis at Naharwan. Arriving near Naharwan, Ali followed his usual method of first exploring the possibilities of a peaceful settlement, but their leader Abdullah bin Wahab al-Rasibi resolved to fight to a finish. In 37/658, Ali marshalled his forces and led the final assault against the Kharijis in the memorable battle of Naharwan, which took place in Shaban, 38/January, 659. With the battle cry, the Kharijis rushed on Ali's troops. All save nine of Abdullah's men were killed and he himself also perished. "A little before this fight" says Simon Ockley in "History of the Saracens" (London, 1870, p. 326), "Ali had foretold to his friends what would be the event. "You see" says he, "these people who make profession of reading the Quran, without observing its commandments, will quit the profession which they make of their sect, as quick arrows fly from the bow when they are shot off."