His followers took this defect to be a sign of the Mahdi and...

His followers took this defect to be a sign of the Mahdi and forged a tradition to that effect. The 'Abbasids also fabricated traditions to bolster their claim to this eminent role predicted about the Mahdi. According to one of these traditions, Ibn 'Abbas reported from the Prophet who said to 'Abbas, his uncle: "At the End of Time there will be Mahdi among you through whom right guidance will spread and the fires of misguidance will be put out.

Indeed, God began this matter with us and will conclude it through your progeny[^11]