When news about disturbances in Egypt reached Ali, he summoned Malik Ashtar to Kufa for consultation. Malik Ashtar was the Commander in Chief of the forces of Ali at the Battle of Siffin. After the Battle of Siffin he was appointed as the Governor of Mesopotamia and was stationed at Nisibin. Ali had his consultation with Qais b Sa'ad about the affairs of Egypt. Ali realized that he had made a mistake in deposing Qais b Sa'ad from the governorship of Egypt. He, however, could not spare Qais to be reposted as governor of Egypt for he wanted him to remain at Kufa by his side as his adviser. He therefore desired Ashtar to accept the offer of governorship of Egypt and restore order. Malik Ashtar was a good military general, and he already commanded influence with the people of Egypt. When Muawiyah came to know of the appointment of Malik Ashtar as a governor of Egypt he felt much concerned. Malik Ashtar was a strong man, and Muawiyah feared that Malik Ashtar would be able to suppress the disturbance in Egypt with a strong hand, and thus frustrate his (Muawiyah's) efforts to wrest Egypt from the control of Ali. Muawiyah accordingly hatched a conspiracy to kill Malik Ashtar before he could reach Egypt. He took into confidence the chief of Qalzaum, a town on the border of Syria and Egypt, and heavily bribed him to kill Malik Ashtar when he arrived there on the way to Egypt. When Malik Ashtar arrived at Qalzaum, the chief of the town waited on him, and provided for his stay in the city for the night. He was well looked after and served with sumptuous meals. Thereafter he was served with a cup of honey, which was poisoned. Malik Ashtar died within a few hours.
When the news of the death of Malik Ashtar reached Damascus, Muawiyah was overjoyed. He announced the news to the people from the pulpit in the main mosque of Damascus. He said that had Ali two arms. One of his arms was 'Amar b Yasir which had been cut in the Battle of Siffin, and with the death of Malik Ashtar his second arm had also been cut off. When Ali came to know to the death of Malik Ashtar he was overwhelmed with grief. The death of his right hand, Malik Ashtar, was a grievous blow for Ali. Ali now seemed to be fighting a losing battle. He was fast losing friends and the number of his enemies was fast multiplying.
When Ali had appointed Malik Ashtar as the governor of Egypt, Muhammad b Abu Bakr felt dissatisfied at his deposition. Ali wrote a letter to Muhammad b Abu Bakr to say that he had passed the order in his interest, for he intended to appoint him as a governor of some other peaceful province where things would be easier for him. With the death of Malik Ashtar, Muhammad b Abu Bakr had to continue in office and bear the brunt of the rebellion of the pro-Othman group from within, and the attack of Muawiyah from without.