Year 37 AH – The engagement at Ṣiffīn:
Muḥammad ibn Saʿd narrated: Muḥammad ibn ʿUmar told us that when ʿUthmān—may Allah be pleased with him—was slain, his wife Nāʾilah wrote to Muʿāwiyah in Syria describing how the assassins had forced their way in and killed him. She also sent him ʿUthmān’s shirt, still stained with blood. Muʿāwiyah read the letter aloud to the people of Syria, and the shirt was carried in procession through the Syrian garrisons. He urged them to seek retribution for ʿUthmān’s blood, and they pledged allegiance to Muʿāwiyah on that basis.
When ʿAlī received the pledge of allegiance as caliph, his son al-Ḥasan and Ibn ʿAbbās said to him, “Write to Muʿāwiyah, confirm him over Syria, and give him hope; he will be satisfied and you will spare yourself trouble from him and his province. Once the people have pledged to you, you may keep him in office or dismiss him as you wish.” ʿAlī replied, “He will not settle for anything less than my giving him Allah’s covenant and binding pledge that I shall never dismiss him.” They said, “Do not grant him that.” News of this reached Muʿāwiyah, who declared, “By Allah, I will not subordinate myself to him, nor will I pledge allegiance to him.” In Syria he publicly announced that al-Zubayr ibn al-ʿAwwām was coming to them and that he would pledge allegiance to al-Zubayr instead. When he heard the outcome of the Battle of the Camel, he held back; and when news of al-Zubayr’s death reached him he invoked mercy upon him, saying, “Had he come to us, we would have given him the pledge, for he was worthy of it.”
After ʿAlī returned from Basra, he sent Jarīr ibn ʿAbd Allāh al-Bajalī to Muʿāwiyah. Jarīr spoke with Muʿāwiyah, impressed upon him the stature of ʿAlī, the oath of allegiance given to him, and the people’s united support, but Muʿāwiyah refused to pledge. A long exchange took place between them. Jarīr then returned to ʿAlī and reported what had happened, so ʿAlī resolved to march toward Syria.
Muʿāwiyah, for his part, dispatched Abū Muslim al-Khawlānī to ʿAlī with several demands, among them the surrender of the killers of ʿUthmān. ʿAlī refused, and correspondence continued between the two sides.