Muslim b. Aqil was the paternal cousin of Imam Husain (peace be on him). He is known in history as the ambassador of the Imam who was martyred in Kufa. He was a well-known and successful soldier and scholar and four of his sons had left Medina in the caravan of Imam Husain. 
The caravan of Imam Husain was on its way to Kufa in 679 CE; the Imam sent Muslim as his ambassador to the people of Kufa with a letter where he addressed them thus: I am sending to you my cousin and one of the most trustworthy person of my household, Muslim b. Aqil, to you so that I may be informed of your affairs. If his reports are in accordance with what you have written to me, I will soon join you. You must know that the Imam is the only (true) follower of God’s Book and he serves God with justice, honesty and truth in all affairs. 
He took his two young sons, Muhammad and Ibrahim, with him to Kufa. Muslim and his sons were welcomed and hosted warmly in Kufa. Very soon, more than 18 thousand people gave allegiance to him. As a result, Muslim wrote a letter to the Imam informing him of the state of affairs in Kufa. 
However, some of Yazid’s spies were also among the people of Kufa and informed him of the events that were occurring there. Yazid ordered one of his governors, Ubaydullah b. Ziyad, to go immediately to Kufa and gave him the orders of capturing and killing Muslim and to do whatever was necessary to put pressure on the followers of Imam Husain (peace be on him) so that they would not support him. 
When Ubaydullah reached Kufa the next morning, he went to the mosque and spoke to the people. He first announced his governorship and then proceeded to threaten to anyone who would work against the government in any way with death and asked them to turn Muslim over to him. He also closed off Kufa so that no one would be allowed to enter or leave the city without the permission of the governor. 
At this time, Muslim was in the house of Hani b. Urwa and no one knew of his presence there except a few people. However, a spy informed Ubaydullah of where he was hiding. Hani was arrested and imprisoned and Muslim, to prevent his friends falling into danger, left Hani’s house with his sons. He sent his sons out of Kufa with Qazi Shorayh so that they may return to Imam Husain through the desert but was unable to leave the city himself. 
Late on the 8th of Dhul Hijjah (the 12th month of the Islamic lunar calendar) Muslim was walking in the outskirts of Kufa and was extremely tired. An old woman was waiting in front of her house for her son to return home. Muslim greeted her and asked her for a glass of water. She complied and upon learning of his identity, she invited him into her home and provided him food and a place to rest. Her name was Tauaa. 
When Tauaa’s son returned home late that night and realized that the person who the governor is after is in his house, he secretly informed Ubaydullah’s people without his mother knowing in order to receive the promised reward. Early the next morning, a large group of soldiers surrounded the house; Muslim left the house, sword in hand and fought valiantly. 
Tired of fighting and injured, he leaned against the wall of the house and the enemy was able to capture him by deceiving him into believing that if he stopped fighting he would be safe. At first he didn’t believe them, but on their insistence he finally laid down his arms. He was surrounded and his sword was taken from him. It was at this moment that he lost hope and started crying. One of the men mocked him and said to him that one who seeks what you seeking (i.e. the reason for his coming to Kufa and what he sought to do) and then gets caught does not cry. Muslim replied: I am not sorrowful for myself… my tears are for my family who are coming towards me and for Husain and his family  (Mufid, p. 361) 
He was taken to Ubaydullah and the promise of safety that he was given was denied by him and he promised he would kill Muslim. Muslim asked to be allowed to make a will and then made it to one  of the people present. He asked him first to pay off a debt that he had when he had come to Kufa, second, he asked that after he was killed, his body be taken from Ubaydullah and buried and third, to send a messenger to Imam Husain asking him to turn back as he had previously written to him telling him that the people are with him and he had no doubt that the Imam was on his way. The first of his requests was met; however, the other two were not carried out. 
The governor gave the order for him to be taken to the terrace of the governing palace and killed. He was taken there all the while reciting supplications and seeking forgiveness and sending salutations to the Prophet Muhammad (peace be on him and his household) and his household and said: O God! You judge between us and these people who betrayed us and lied to us and did not help us. They then beheaded him and threw his head down the building, with his body following (Mufid, pp. 363-366). 
According to some historians (and contrary to what was promised by the governor), the bodies of Muslim and Hani, who was killed after him, were dragged through the bazaars of Kufa (Qummi, p. 100).


http://www.eslam.de/begriffe/m/muslim_ibn_aqil.htm 
Mufid, Muhammad. 1388 AP. Tarjuma-yi Irshād-i Shaykh Mufīd, Sire-yi Aimme-yi Aṭhar [a translation of Shaykh Mufid’s Irshad on the conduct of the Imams]. (Hasan Musawi Mujab, Trans.). Qom: Surur Publications. 
Qummi, Abbas. 1381 AP. Damʿ al-Sujūm: Tarjume-yi Kitāb-i Nafasul Mahmūm [translation of Abbas Qummi’s Nafasul Mahmum]. (Abul Hasan Shaʿrani, Trans.). Qom: Hijrat Publications.


Compiled by: N. Bayani
Translated by: Rashed