A possible member of the artisan guild,[1] Haidar Qassāb served in the government of Khwaja Shams al-Din 'Ali as a collector of urban craft and trade taxes.
When the accounts for the revenues generated by these taxes fell into arrears, Haidar was harshly punished by Shams al-Din 'Ali.
Yahya Karawi, an aristocrat who had been informed by Haidar of the assassination plot, succeeded Shams al-Din 'Ali as head of state.
Haidar Qassāb prevented this by marching from Astarabad to Sabzewar and forcing the conspirators to flee the city.
[2] Before he and his army could reach Esfarayen to subdue the rebels, he was stabbed to death by the Turkish slave of Hasan Damghani in 1356.