Al-Saffāḥ then appointed his brother Abū Jaʿfar al-Manṣūr governor of al-Jazīrah, Adharbayjan, and Armenia, and he remained over those provinces until the caliphate devolved upon him after his brother’s death. It is said that Isḥāq ibn Muslim al-ʿUqaylī did not seek safe-conduct until he was certain that Marwān had been killed—seven months into the siege. Because he had been a companion of Abū Jaʿfar al-Manṣūr, the latter granted him amnesty.

In this same year Abū Jaʿfar al-Manṣūr, acting on his brother al-Saffāḥ’s orders, traveled to Abū Muslim al-Khurasānī, the governor of Khurasān, ⦗1⦘ to learn his view on killing Abū Salamah Ḥafṣ ibn Sulaymān, the vizier. The reason was that al-Saffāḥ had spent an evening in conversation with his family and recalled Abū Salamah’s earlier attempt to divert the caliphate from the Banū al-ʿAbbās. Someone asked, “Did Abū Muslim aid and abet Abū Salamah in that or not?” The gathering fell silent. Al-Saffāḥ remarked, “If this was indeed his counsel, we are on the brink of a grave ordeal—unless Allah wards it from us.”

Abū Jaʿfar relates: “My brother then said to me, ‘What is your opinion?’ I replied, ‘The decision is yours.’ He said, ‘No one is closer to Abū Muslim than you. Go to him, find out the truth for me; if it was on his advice we shall contrive a plan against him, and if not, our minds will be at ease.’ So I set out, fearful at heart.

“Upon reaching al-Rayy I found a letter from Abū Muslim to his deputy urging him to hasten my journey, which only increased my anxiety. When I arrived in Naysābūr there was another such letter in which he instructed the deputy, ‘Do not let him remain even an hour, for your land is rife with Kharijites.’ That lifted my spirits somewhat. When I came within two farsakhs of Marw, he rode out to meet me with the people; on seeing me he dismounted and kissed my hand, and at my bidding remounted. After I had entered Marw and lodged in his residence, three days passed and he did not ask why I had come.

“On the fourth day he said, ‘What has brought you?’ I informed him. He exclaimed, ‘Was it Abū Salamah who did that? I shall relieve you of him!’ He then summoned Marrār ibn Anas al-Ḍabbī and said, ‘Go to Kufa; wherever you meet Abū Salamah, kill him, and act according to the Imam’s judgment.’ Marrār arrived at al-Kūfa al-Hāshimiyyah while Abū Salamah was spending the evening with al-Saffāḥ. When he came out, Marrār killed him. It was rumored that the Kharijites had done it. The city’s gates were shut; afterward Yaḥyā ibn Muḥammad ibn ʿAlī, the Caliph’s brother, led the funeral prayer over him and he was buried at al-Hāshimiyyah. People called him ‘the vizier of the House of Muḥammad,’ just as they called Abū Muslim ‘the commander of the House of Muḥammad.’

A poet said:
The vizier—the vizier of the House of Muḥammad—is gone;
thus, whoever envied you now wears the vizier’s cloak.

It is also reported that Abū Jaʿfar did not set out to Abū Muslim until after Abū Salamah’s death. He traveled by the postal relay with thirty men, among them al-Ḥajjāj ibn Arṭāʾah, Isḥāq ibn al-Faḍl al-Hāshimī, and a number of notables.

When Abū Jaʿfar returned from Khurasān he said to his brother, ‘You are no caliph as long as Abū Muslim lives; you must kill him,’ for he had seen how the armies and commanders obeyed Abū Muslim. Al-Saffāḥ replied, ‘Keep that to yourself,’ and Abū Jaʿfar fell silent. Later al-Saffāḥ sent his brother Abū Jaʿfar to fight Ibn Hubayrah at Wāsiṭ. On the way he took al-Ḥasan ibn Qaḥṭabah with him, and when Ibn Hubayrah was surrounded he wrote to Muḥammad ibn ʿAbd Allāh ibn al-Ḥasan asking him to pledge allegiance to him.