agreement with Mu'awiya. Similar statements are attributed to Ali by Ibn Muzahim and Ibn Abi'l-Hadid, in which the caliph vows to uphold the covenant with Mu'awiya. In another account by al-Tabari, Ali cites verse 16:91 for upholding the treaty when two Kharijites, namely, Zur'a ibn al-Burj al-Ta'i and Hurqus ibn Zuhayr al-Sa'di, appealed to him to revoke it. Many of the dissidents apparently accepted Ali's position, while the rest left for al-Nahrawan, a town near al-Mada'in, and there declared Abd-Allah ibn Wahb al-Rasibi () as their leader. These formed the Kharijites (), who later took up arms against Ali in the Battle of Nahrawan (658). They soon labeled anyone who opposed them as nonbelievers, who had to be fought, thus becoming the forerunners of Islamic extremism, according to some. Their motives Donner suggests that the seceders, among them many of the , may have feared being held accountable for their role in the assassination of Uthman. Alternatively, Hinds and Poonawala believe that the seceders were disillusioned with the arbitration process, particularly by the removal of Ali's title of in the final agreement and by its reference to the Sunna next to the Quran, as noted also in Waq'at Sifin. After being silent about it initially, the Syrians now said that they also wanted the arbitrators to judge whether the killing of Uthman was justified, about which the had no doubts. Hinds and Poonawala thus regard the arbitration as a skilfully-planned manoeuvre to disintegrate the coalition of Ali. For Ayoub, the seceders were frustrated with a costly war that had achieved nothing and denounced the agreement that questioned the authority of the legitimate Muslim caliph, in their view. Their slogan The seceders adopted the slogan, "No judgment but that of God," highlighting their rejection of the arbitration (by men) in reference to the Quranic verse 49:9, "If two parties of the Believers fight with one another, make peace between them; but if one rebels against the other, then fight against the one that rebels, until they return to obedience to God." When they interrupted Ali's sermon with this slogan, he commented that it was a word of truth by which the seceders sought falsehood. He added that they were repudiating government even though a ruler was indispensable in the conduct of religion. Ali nevertheless did not bar their entry to mosques or deprive them of their shares in the treasury, saying