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HISTORY
Abū ʿAbd Allāh Muḥammad ibn ʿAbd Allāh al-Mahdī , was the third Abbasid Caliph who reigned from 775 to his death in 785. He succeeded his father, al-Mansur.
Wikipedia contributors, "al-Mahdi," Wikipedia, The Free Encyclopedia,
ABOUT THE ARABIC LANGUAGE