According to al-Tabari, who preserves the fullest account of the events,[1] the uprising began when a soldier wanted to billet himself in Abu Harb's house during his absence.
In the year of his revolt, Syrian agriculture had been ruined due to a severely cold and dry winter followed by an especially stormy spring during which the harvests were wiped out by locusts.
The historian Paul Cobb surmises that these conditions may have contributed to the appeal of Abu Harb's message of popular justice and low taxation among the peasantry.
Al-Hidari's forces were considerably outnumbered, and the Abbasid general wisely decided to wait until the harvest season, when perforce the bulk of al-Mubarqa's peasant supporters would disperse to their fields.
Al-Tabari on the other hand places the rebellion and its defeat squarely within the reign of al-Mu'tasim, i.e., before his death on 5 January 842, and records Ibn Bayhas as an adherent of al-Mubarqa.