About the year A.H. 134 (751) the new Caliph’s brother paid an official visit to Merv, in order to report on the state of the Eastern provinces. So much alarmed was he at the influence and independence of Abū Muslim that on his return to Kufa he recommended his brother to rid himself of the man to whom he owed his throne. In the following year Ziyād, the governor of Samarkand, probably at the instigation of the Caliph, rose against Abū Muslim; but the movement was quickly crushed, and Ziyād was deposed and put to death. In the following year, A.H. 136 (753), while Abū Muslim and Abū Ja`far were returning from a pilgrimage to Mekka, the Caliph es-Saffāh died in Anbār. Abū Ja`far, who is well known in history as El-Mansūr, had been designated by his brother to succeed him,[182] but he had a rival in the person of his uncle `Abdullah, who was at the head of a considerable army, including a contingent of 17,000 men of Khorāsān. Abū Muslim, compelled to choose between the pretenders, declared for Abū Ja`far, whereupon `Abdullah caused a massacre of the whole of his Khorāsān contingent,[183] in the knowledge that they would refuse to draw the sword against the governor of their province. But the precaution was of no avail, for shortly afterwards his Syrian army was utterly defeated near Nisibis by a Persian force under Abū Muslim, and `Abdullah was compelled to abandon his claim. Hardly was this danger averted when the Caliph el-Mansūr again allowed his jealousy of Abū Muslim to get the better of him. Abū Muslim was warned of his ill-will, so resolved an immediate return to Khorāsān. In order to prevent this the Caliph appointed him to the governorship of Syria and Egypt, and invited him to an audience in Madā´in. The correspondence[184] which followed between the Caliph and his too powerful lieutenant gives us a graphic picture of the times, and also possesses some historical importance. Abū Muslim was too wary to accept the Caliph’s invitation. “A certain king of the Sāsānides,” he replied, “once said: ‘There is no more dangerous time for a Vezīr than when complete tranquillity reigns in the kingdom.’ ... I therefore deem it expedient to avoid the proximity of the Commander of the Faithful, without, however, ceasing on this account to be his faithful subject. Should the Commander of the Faithful allow me to do so I will be the most humble of his servants, but if he gives vent to his passions I shall be compelled for my own safety to recall my allegiance.”