Zaydis believe Zayd ibn Ali was the rightful successor to the Imamate because he led a rebellion against the Umayyad Caliphate, who he believed were tyrannical and corrupt. Muhammad al-Baqir did not engage in political action and the followers of Zayd believed that a true Imām must fight against corrupt rulers. The renowned Muslim jurist Abu Hanifa who is credited for the Hanafi school of Sunni Islam, delivered a fatwā or legal statement in favour of Zayd in his rebellion against the Umayyad ruler. He also urged people in secret to join the uprising and delivered funds to Zayd.