The office of "amir al-ʿarab" passed to Muhanna's son Sharaf ad-Din ʿIsa, though it is not clear which Mamluk sultan bestowed the title upon him. According to several Mamluk-era sources, Sultan Qutuz (r. 1259–1260) appointed ʿIsa in the aftermath of the Mamluk victory over the Mongols at the Battle of Ayn Jalut. However the 14th-century Arab historian al-ʿUmari claims Qutuz's successor Baybars made ʿIsa "amir al-ʿarab". This was apparently a reward for ʿIsa's aid and friendship during Baybars' exile in Syria in the 1250s at a time when Abu Bakr's father Ali denied him refuge. Whatever the correct version, Baybars at least confirmed ʿIsa's appointment and his "iqtaʿat" (fiefs) in 1260/61. Abu Bakr's brother Zamil and Tahir ibn Ghannam's son Ahmad both contested ʿIsa's appointment. The latter requested a share in the emirate, but Baybars gave him a smaller emirate elsewhere in Syria instead, while Zamil revolted to gain full control of ʿIsa's emirate. Zamil was defeated by ʿIsa and the Mamluks and was imprisoned in Cairo. He was later released and a temporary peace was mediated between him, ʿIsa and other emirs of the Banu Rabi'ah. ʿIsa's strongest Bedouin opposition came from his kinsmen in the Al Mira under the leadership of Ahmad ibn Hajji, who dominated the tribes of southern Syria. Gradually, the enmity between the Al Fadl and the Al Mira dissipated as Ahmad was given virtual independence in the southern desert, while ʿIsa remained "amir al-ʿarab".