 According to Shia belief, Harun imprisoned and poisoned Musa ibn Ja'far, the 7th Imam, in Baghdad.Hārūn was influenced by the will of his incredibly powerful mother in the governance of the empire until her death in 789.His vizier (chief minister) Yahya the Barmakid, Yahya's sons (especially Ja'far ibn Yahya), and other Barmakids generally controlled the administration.