al-Fihri, the governor of Damascus, meanwhile, threw his backing behind Ibn al-Zubayr. During the Battle of Marj Rahit, which pitted Marwan against Dahhak in a meadow north of Damascus, the scion of the Ghassanid family in Damascus, Yazid ibn Abi al-Nims, led a revolt there and secured control of the city for Marwan, who routed Dahhak and assumed office. In a poem attributed to him, Marwan lauds the Ghassan, as well as the Kalb, Kinda, and Tanukh of Syria, for supporting him. The above tribes thereafter formed the Yaman faction, in opposition to the Qays tribes which backed Dahhak and Ibn al-Zubayr. The Qays–Yaman rivalry contributed to the downfall of Umayyad rule, with each faction supporting different Umayyad dynasts and governors in what became the Third Muslim Civil War. The Ghassanid Shabib ibn Abi Malik was a leader of the Yaman in Damascus and conspired to assassinate the pro-Qaysi Caliph al-Walid II (). After the latter was killed, the Ghassan marched on Damascus to help install his successor, the Yamani-backed Yazid III (). The toppling of the Umayyads and the advent of the Iraq-based Abbasid Caliphate in 750 "was disastrous for the power, wealth and status of the Arab tribes in Syria", including the Ghassan, according to the historian Hugh N. Kennedy. By the 9th century, the tribe had adopted a settled life, being recorded by the geographer al-Ya'qubi (d. 890) to be living in the Ghouta gardens region of Damascus and in Gharandal in Transjordan. Scholarly families in Damascus Two Damascene Ghassanid families in particular achieved prominence in early Islamic Syria, those of Yahya ibn Yahya al-Ghassani (d. 750s) and Abu Mushir al-Ghassani (d. 833). The former was the son of Caliph Marwan's head of the shurta, Yahya ibn Qays. Upon returning to Damascus after his stint as a governor of Mosul for the Umayyad caliph Umar II (), Yahya ibn Yahya took up scholarship and became known as the sayyid ahl Dimashq (leader of the people of Damascus), transmitting purported hadiths (traditions and utterances) of Muhammad, which he derived from his uncle Sulayman, who received the transmissions from Muhammad's Damascus-based companion, Abu Darda. Among some traditions sourced to Yahya ibn Yahya by later Muslim scholars are those regarding the discovery of John the Baptist's head in the Umayyad Mosque of Damascus and others which praise the mosque's splendor and the Umayyad dynasty in general. Yahya ibn Yahya's sons,