Abu Saeed Khudri reported,

While we were with the Messenger of Allah ﷺ as he was distributing some spoils, Dhul-Khuwaysirah, a man from Banu Tamim, came to him and said, "Messenger of Allah, be just."The Prophet ﷺ replied, "Woe to you. Who would be just if I am not? I would surely be lost and ruined if I were not just."Umar said, "Messenger of Allah, allow me to strike off his neck."The Prophet ﷺ said, "Leave him. He has companions whose prayer any of you would consider insignificant compared to theirs, and whose fasting would seem trivial compared to theirs. They recite the Quran, but it does not pass beyond their throats. They will pass through the religion the way an arrow passes through its prey. One looks at the arrow's tip and finds nothing on it, then looks at its shaft and finds nothing, then looks at its arrow-stick and finds nothing, then looks at its feathers and finds nothing. The arrow has shot clean through, faster than the dung and blood could cling to it. Their distinguishing sign is a black man, one of whose upper arms is like a woman's breast, or like a quivering piece of flesh. They will appear at a time of division among the people."Abu Saeed said, "I bear witness that I heard this hadith from the Messenger of Allah ﷺ, and I bear witness that Ali bin Abu Talib fought them while I was with him. He ordered that the described man be sought out, and he was brought, until I looked at him exactly as the Prophet ﷺ had described him."

عن أبي سعيد الخدري قال

بينما نحن عند رسول الله ﷺ وهو يقسم قسما، أتاه ذو الخويصرة، وهو رجل من بني تميم، فقال: يا رسول الله اعدل، فقال: ويلك، ومن يعدل إذا لم أعدل، قد خبت وخسرت إن لم أكن أعدل. فقال عمر: يا رسول الله، ائذن لي فيه فأضرب عنقه؟ فقال: دعه، فإن له أصحابا يحقر أحدكم صلاته مع صلاتهم، وصيامه مع صيامهم، يقرؤون القرآن لا يجاوز تراقيهم، يمرقون من الدين كما يمرق السهم من الرمية، ينظر إلى نصله فلا يوجد فيه شيء، ثم ينظر إلى رصافه فما يوجد فيه شيء، ثم ينظر إلى نضيه- وهو قدحه- فلا يوجد فيه شيء، ثم ينظر إلى قذذه فلا يوجد فيه شيء، قد سبق الفرث والدم، آيتهم رجل أسود، إحدى عضديه مثل ثدي المرأة، أو مثل البضعة تدردر، ويخرجون على حين فرقة من الناس. قال أبو سعيد: فأشهد أني سمعت هذا الحديث من رسول الله ﷺ، وأشهد أن علي بن أبي طالب قاتلهم وأنا معه، فأمر بذلك الرجل فالتمس فأتي به، حتى نظرت إليه على نعت النبي ﷺ الذي نعته.