It is narrated from Habib bin Abi Thabit; he said: I came to Abu Wa'il while he was in the mosque of his neighbourhood, and we sat apart in a corner of the mosque. I said to him: "Will you not tell me about those people (the Khawarij) whom Sayyiduna Ali (may Allah be pleased with him) killed? Over what did they part from him, on what basis did they join him when he called them, and then, when they separated from him, why did he consider fighting them lawful?" He said: When we were at Siffin, the killing became fierce among the people of Sham, then he narrated the whole story.
He said: Then Sayyiduna Ali (may Allah be pleased with him) returned to Kufah, and the Khawarij said about him what they said, and they camped at the village called "Harura'", and they were somewhat more than ten thousand. Sayyiduna Ali (may Allah be pleased with him) sent a message to them, adjuring them by Allah Almighty: "Return to your Caliph. What do you resent in him? Is it the distribution of wealth, or a judgement?" They said: "We fear that we may fall into a fitnah (trial)." He said: "Do not hasten into this year's misguidance out of fear of next year's fitnah." So they went back and said: "Let him be (watched) from our side: if he accepts the (arbitration) decision, we will fight him on the same basis on which we fought the people of Sham at Siffin, and if he breaks it, we will fight alongside him." Then they marched until they crossed Nahrawan, and a group of them broke away and began killing people. Their companions said: "It was not for this that we separated from Ali." When news of their deed reached Sayyiduna Ali (may Allah be pleased with him), he stood up and said: "Will you march against your enemy (the people of Sham), or will you turn back to these people who have stayed behind you in your lands (causing havoc)?" The people said: "Rather, we will turn back to them (the Khawarij)." The narrator said: At that point Sayyiduna Ali (may Allah be pleased with him) narrated that the Messenger of Allah (peace and blessings be upon him) said: "A group will emerge from the direction of the east at a time of disagreement among the people. They will regard your jihad as nothing compared with their jihad, your prayer as nothing compared with their prayer, and your fasting as nothing compared with their fasting. They will pass out of the religion as an arrow passes through the game. Their sign will be a man whose upper arm is like a woman's breast (a lump of flesh). They will be killed by whichever of the two groups is closer to the truth."
Then Sayyiduna Ali (may Allah be pleased with him) advanced against them and fought them fiercely. The horsemen of Sayyiduna Ali (may Allah be pleased with him) held back before them, so he said: "O people! If you are fighting them only for my sake, then by Allah, I have nothing to tell you; but if you are fighting only for the sake of Allah Almighty, then your fighting should not be like this (weak)." So they fell upon them and killed them all. Then he said: "Search for him (the marked man)." They searched for him but he was not found. Then Sayyiduna Ali (may Allah be pleased with him) mounted his riding animal and reached a hollow in the ground where the slain lay heaped one upon another. He was pulled out from beneath them and dragged by his foot so that the people could see him. Then Sayyiduna Ali (may Allah be pleased with him) said: "I will not go on any campaign this year." Then he returned to Kufah and (some time later) he was martyred there.
Then the people made Sayyiduna al-Hasan bin Ali (may Allah be pleased with them both) the Caliph. Sayyiduna al-Hasan (may Allah be pleased with him) sent his pledge of allegiance to Sayyiduna Mu'awiyah (may Allah be pleased with him), and al-Hasan also wrote about this to Qays bin Sa'd (may Allah be pleased with them both). Qays bin Sa'd (may Allah be pleased with him) stood up among his companions and said: "O people! Two matters have come before you, and you must take one of them: either entering into fitnah, or being killed without an imam." The people asked: "What is this matter?" He said: "Al-Hasan bin Ali has given his pledge of allegiance to Mu'awiyah." So the people went back and pledged allegiance to Sayyiduna Mu'awiyah (may Allah be pleased with him). Sayyiduna Mu'awiyah's (may Allah be pleased with him) only concern now was those who remained at Nahrawan. They began coming over to him one by one and pledging allegiance to him, until only three hundred and some of them remained, and they were the people of al-Nukhaylah.
I (Ibn Hajar) say: Its chain is sahih (authentic).
Abu Bakr also narrated it from Abdullah bin Numayr, from Abd al-Aziz bin Siyah, with the same chain.
Abu Ya'la also narrated it from Abu Bakr bin Abi Shaybah, with the same chain.
The original marfu' part of this hadith is in Sahih Muslim and elsewhere. I have quoted it here because it contains additions over the routes that the authors of the six books and Imam Ahmad also recorded.
Hadith Referenceالمطالب العالية بزوائد المسانيد الثمانية / كتاب الفتوح / 4439
Hadith Gradingمحدثین:إسناده صحيح
Hadith Takhrij«حکم الحدیث المطالب العالیہ محققاً تنسیق د. سعد بن ناصر بن عبد العزيز الشَّثري- مکتبہ شاملہ :قال ابن حجر: هَذَا الْإِسْنَادُ صَحِيحٌ . » «أخرجه صحيح مسلم برقم: 1066، وأخرجه صحيح ابن حبان برقم: 6938، وأخرجه المستدرك للحاكم برقم: 8712، وأخرجه السنن الكبرى للنسائي برقم: 8509، وأخرجه سنن أبي داود برقم: 4763، وأخرجه سنن ابن ماجه برقم: 167، وأخرجه السنن الكبرى للبيهقي برقم: 4010، وأخرجه سنن الدارقطني برقم: 3250، وأخرجه مسند أحمد برقم: 636، وأخرجه مسند الطيالسي برقم: 160، وأخرجه مسند الحميدي برقم: 59، وأخرجه مسند أبي يعلى برقم: 337، وأخرجه مسند البزار برقم: 539، وأخرجه المطالب العالية لابن حجر برقم: 4435 / 1، وأخرجه مصنف عبد الرزاق برقم: 5962، وأخرجه مصنف ابن أبي شيبة برقم: 8510، وأخرجه شرح مشكل الآثار للطحاوي برقم: 4065، وأخرجه المعجم الصغير للطبراني برقم: 969، وأخرجه المعجم الأوسط للطبراني برقم: 1537»