Translation: Ishaaq bn AbdirRaheem Aboo Aamir
The Battle of Nahrawaan left a deep scar in the minds of the Khawaarij; thus the each passing of the days and nights only increased them in their pains and woes. Thus a group of them agreed that they would see an end to Alee's life. They wanted to do that so as to take revenge for their comrades that were killed at Nahrawaan. The historians and chroniclers agreed over a popular report which is not safe from criticism (as to its authenticity) because of what it contains of various (incongruent) elements and other different things. We do not deny the fact that the great event (of killing of Alee (may Allâh be pleased with him)) could call for additions and modifications in the later times (in history). It has come to the fore from sources and studies that there is an agreement (by the historians of the Deen) that the event of the killing of Alee (may Allâh be pleased with him) was orchestrated and actualized by some rebellious elements who were taking revenge for the victims of the Nahrawaan Battle.
[See: At-Tabaqaat ibn Sa'd (3/35), Taareekh At-Tabaree (6/58-66) with a broken chain; Mar'waj Adh-Dhahab (3/423), Al-Kabeer of Tabaraanee (1/55-85), Majmauz-Zawaaid (6/249), Taareekhul-Islaam Wal-Khulafaaur-Raashideen, p.749; Wafayaat Al-A'yaan (7/318), Al-Bidaayah Wa Nihaayah (7/325).]
As for other known things with respect to the murder of Alee (may Allâh be pleased with him) such as the story of the love between Ibn Muljam and Qattaam and the alleged role played by Al-Ash'ath Al-Kindee. The explanation as regard its innocence in that shall come by the Will of Allâh ( later in this work); so also so other additions which might be difficult to accept and hold as the truth. But here is how Alee (may Allâh be pleased with him) was killed:
The meeting of the conspirators: That comes to the open in the conversation of Ibn Muljam and his associates; that Ibn Muljam, Al-Bur'k bn Abdullah, Amr Bakr At-Taymee met and discussed the affair of the people. They decried the leaders after which they mentioned the people that were killed at Nahrawaan; they asked mercy for them and said: 'We have done nothing for those who were left after them; those were our brethren who used to call the people to the worship of their Lord and those would not fear anybody's rebuke with respect to Allâh; if we could sell our souls and go to the leaders of misguidance and kill them then we would be able to relieve the land of them and we would have revenged the death of our brethren.'
Then Ibn Muljam said: 'I will suffice you with regard to Alee bn Taalib.' Ibn Muljam was from the people of Egypt. Al-Bur'k bn Abdullah said: 'I will suffice you with regard to Muawiyah.' Amr bn Abee Bakr said: 'I will suffice you with regard to Amr bn Al-Aas.' Then they entered into a mutual agreement and covenanted in the Name of Allâh that none of them would fail to carry out his own assignment which he had sworn to carry out – either each of them killed their target or he was killed instead, thus they took their swords which they began to poison and prepared for the seventeen remaining days in the month of Ramadan after which each of them would go after his prey. And each of them began to move towards the city where their targets were so as to seek them.
[See: Taareekh At-Tabaree (6/59).]