Cruel and treacherous, like most of his family, Abú Ja‘far Manṣúr was perhaps the greatest ruler whom the ‘Abbásids produced.[483] He had to fight hard for his throne. The ‘Alids, who deemed themselves the true heirs of the Prophet in virtue of their descent from Fáṭima, rose in rebellion against the usurper, surprised him in an unguarded moment, and drove him to such straits that during seven weeks he never changed his dress except for public prayers. But once more the ‘Alids proved incapable of grasping their opportunity. The leaders, Muḥammad, who was known as 'The Pure Soul' (_al-Nafs al-zakiyya_), and his brother Ibráhím, fell on the battle-field. Under Mahdí and Hárún members of the House of ‘Alí continued to 'come out,' but with no better success. In Eastern Persia, where strong national feelings interwove themselves with Pre-Muḥammadan religious ideas, those of Mazdak and Zoroaster in particular, the ‘Abbásids encountered a formidable opposition which proclaimed its vigour and tenacity by the successive revolts of Sinbádh the Magian (755-756 A.D.), Ustádhsís (766-768), Muqanna‘, the 'Veiled Prophet of Khurásán' (780-786), and Bábak the Khurramite (816-838).[484] [Sidenote: Manṣúr's advice to Mahdí.] Manṣúr said to his son Mahdi, "O Abú ‘Abdalláh, when you sit in company, always have divines to converse with you; for Muḥammad b. Shiháb al-Zuhrí said, 'The word _ḥadíth_ (Apostolic Tradition) is masculine: only virile men love it, and only effeminate men dislike it'; and he spoke the truth."[485] [Sidenote: Manṣúr and the poet.] On one occasion a poet came to Mahdí, who was then heir-apparent, at Rayy, and recited a panegyric in his honour. The prince gave him 20,000 dirhems. Thereupon the postmaster of Rayy informed Manṣúr, who wrote to his son reproaching him for such extravagance. "What you should have done," he said, "was to let him wait a year at your door, and after that time bestow on him 4,000 dirhems." He then caused the poet to be arrested and brought into his presence. "You went to a heedless youth and cajoled him?" "Yes, God save the Commander of the Faithful, I went to a heedless, generous youth and cajoled him, and he suffered himself to be cajoled." "Recite your eulogy of him." The poet obeyed, not forgetting to conclude his verses with a compliment to Manṣúr. "Bravo!" cried the Caliph, "but they are not worth 20,000 dirhems. Where is the money?" On its being produced he made him a gift of 4,000 dirhems and confiscated the remainder.[486] [Sidenote: The Barmecides.] [Sidenote: Yaḥyá b. Khálid.]