Kammala wannan jumla: Fadl ya fara aikinsa a zamanin Harun al-Rashid (r. 786<unk>809) a matsayin mai riƙe da Harthama ibn A'yan, a lokacin shugaban masu tsaron gidan kalifa. Kwarewar sa ta gudanarwa ta jawo hankalin Harun, wanda ya nada shi sakatare a cikin "diwan al-kharaj" ("Ofishin Harajin Kasa"). A lokacin da
yakin basasa da ya biyo bayan mutuwar Harun, Fadl ya yi ritaya zuwa ga dukiyarsa a Iraki. A can ne Abu Ishaq, ƙaramin ɗan'uwan Halifa al-Ma'mun (r. 813 <unk> 833) da kuma Caliph al-Mu'tasim na gaba, wanda ya ba da ƙwarewar masaniyar haraji da aikin gona. A shekara ta 828, Abu Ishaq ya dauke shi zuwa Masar sannan ya nada shi shugaban "diwan al-kharaj".