Jammaz sought the assistance of an-Nasir Yusuf, the Ayyubid Sultan of Damascus, against his cousin Abu Sa'd al-Hasan, the Emir of Mecca.
Supported by Syrian troops Jammaz entered Mecca in Ramadan 651 AH (October/November 1253) and deposed and killed Abu Sa'd.
[a] However, he reneged on his promise to put al-Nasir's name in the khutbah, and instead continued the khutbah in the name of the Sultan of Yemen, al-Muzaffar Yusuf.
On the last day of Dhu al-Hijjah (c. 20 February 1254) his uncle Rajih ibn Qatadah took the Emirate from him without resistance, and Jammaz fled to Yanbu.
The later Emirs of Yanbu were from among his progeny.