A group of the Kharijites gathered at Mecca and they mentioned the leaders (of the people) and blamed them and their actions. They mentioned the people of al-Nahrawan and they asked God's mercy for them. Then they said to each other: "If (only) we devoted ourselves to God, and went to the leaders (Imams) of error (dalal) and sought a moment when they were inattentive and then rid the country and men of them for the sake of God, and also avenged our brothers, the martyrs of al-Nahrawan."
They made a compact to do that after performing the pilgrimage. 'Abd al-Rahman ibn Muljam (LA), said: "I'll take care of (killing) 'Ali for you." Al-Burak ibn 'Abd Allah al-Tamimi said: "I will take care of (killing) Mu'awiya for you." 'Amr ibn Bakr al-Tamimi said: "I will take care of (killing) 'Amr ibn al-'As for you." They made a compact to do that and bound themselves to its fulfilment. They agreed to carry it out on the night of the 19th of the month of Ramadan. On that they separated.
Ibn Muljam, may God curse him, set out - he was numbered among Kinda - until he came to Kufa. There he met his colleagues. But he kept his task secret from them out of fear that something of it might get spread around. The situation was like this when one day he visited one of his colleagues from Taym al-Rabab. At this man's house he met by chance Qatam, daughter of al-Akhdar of Taym. The Commander of the faithful, peace be on him, had killed her father and brother at al-Nahrawan. She was (also) one of the most beautiful of the women of her time. When Ibn Muljam, may God curse him, saw her, he fell in love with her and his admiration of her became very intense. He asked to marry her and became engaged to her. Then she said to him: "What dowry do you suggest for me?"
"Make your decision on that," he answered.
"I have decided," she said, "that you should (give me three thousand dirhams, a young serving boy, a servant and the murder of 'Ali ibn Abi Talib."
"You can have all you asked for," he replied. "But as for the murder of 'Ali ibn Abi Talib, how can I do that?"
"You should look (for a time) when he is careless," she said. "If you kill him, I will cure myself (of my obsession against him) and life with me will be a pleasure for you. If you are killed, God has nothing in this world which is better for you (than such a death)."
"The only thing which has brought me to this town (misr)," he said, "when I was a fugitive from it and could find no protection with its inhabitants, was to kill 'Ali b. Abi Talib, which you have asked me for. So you will have what you have asked for."
"I have been looking for someone to help you and strengthen you in that (undertaking)," she said. Then she went to Wardan ibn Mujalid from Taym al-Rabab. She gave him the information and asked help for Ibn Muljam, may God curse him. He undertook to share responsibility for that for her.
Then Ibn Muljam, may God curse him, went out and came to a man from Ashja' called Shabib ibn Bajura and said to him:
"Shabib, would you like nobility (sharaf) in this world and the next life?"
"What is that?" he asked.
"Will you help me to kill 'Ali b. Abi Talib?"
Shabib was one who held the view of the Kharijites, so he said to Ibn Muljam: "May a wailing woman wail for you (at your death), Ibn Muljam. For you have come to something which is horrific. How will you be able to do it?"
"We will lie in wait for him in the great mosque," Ibn Muljam, may God curse him, replied. "Then when he comes to the dawn prayer, we will attack him. If we kill him, we will satisfy ourselves and attain our vengeance."
He insisted until he agreed and went with him into the great mosque to Qatam, while she was performing the rite of i'tikaf there and put up a tent. They both said to her: "We have reached agreement on killing this man."
"When you want (to do) that," she said, "come to me in this place."
Then they left her and waited for several days. They came to her finally on the night of Wednesday, the 19thof the month of Ramadan in the year 40 AH. She ordered some silk which she tied around their chests. They put on their swords, and went out and sat opposite at the door from which the Commander of the faithful, peace be on him, would come out to the prayer. However before that, they had told al-Ash'ath ibn Qays of the resolution in their spirits to kill the Commander of the faithful, peace be on him. Al-Ash'ath ibn Qays, may God curse him, agreed with them in what they had agreed upon.
Hujr ibn 'Adi, may God have mercy on him, was (also) spending that night in the mosque. He overheard al-Ash'ath saying to Ibn Muljam:
"Hurry, hurry to your task, for dawn is beginning to appear."
Hujr perceived the intention of al-Ash'ath and said to him: "You are going to kill him, you one-eyed man."
He left directly to go to the Commander of the faithful, peace be on him, and tell him the news to warn him about the group. However, the Commander of the faithful, peace be on him, missed him on the way and went into the mosque. Ibn Muljam came to him first and struck him. Hujr approached as the people were crying: "The Commander of the faithful has been killed!"
As for the two men who were in agreement with Ibn Muljam to kill Mu'awiya and 'Amr ibn al 'As, the one struck Mu'awiya while he was bending (in prayer). However his blow was delivered weakly and he was saved from its consequences. The man was seized and killed immediately.
As for the other he went to carry out his mission that night. However 'Amr had felt sick and had put a man in his place to pray with the people; the man was called Kharija ibn Abi Habiba al-'Amiri. He struck with his sword when he thought that it was 'Amr. He was seized and taken to 'Amr who had him killed. Kharija died on the second day!
Reference: Kitab al-Irshad, Sheikh Mufid