But among those who entered the ranks of the dynasty were people whose inward convictions its rulers did not approve of, and others whom they could not keep out, just as Alī could not restrain the commanders who were the leading figures in his army, such as al-Ashath ibn Qays, al-Ashtar al-Nakhaī, Hāshim al-Mirqāl, and others like them.
Among those who entered were descendants of the Magians, as well as religious innovators and heretics who harbored resentment against Islam. Al-Mahdī hunted them down and put them to death (1), thereby warding off a great evil (2). He was among the best caliphs of Banū al-Abbās.
Likewise, al-Rashīd (3) held learning, jihad, and religion in such esteem that his reign was among the best reigns of Banū al-Abbās. It was as though it marked the culmination of their good fortune, for their affairs fell into disorder afterward. Yet none of the Abbasids ever gained control of al-Andalus or most of the Maghrib. Some of them ruled Ifrīqiya for a time, but it was subsequently taken from them.
Those earlier rulers, by contrast, controlled the entire Islamic realm and subdued all the enemies of the religion. They had an army in al-Andalus conquering it, an army in the lands of the Turks fighting the Great Qān (4), an army in the lands of the slaves (5), and an army in Byzantine territory. Islam was expanding and growing stronger, enjoying might throughout the earth.
This confirms what the Prophet—may Allah bless him and grant him peace—foretold when he said:
“Never