Musannaf Ibn Abi Shaybah 40713 — Reports on the Khawarij

Bishr bin Shaghaf said: Sayyiduna Abdullah bin Salam (may Allah be pleased with him) asked me about the Khawarij, and I said: "They are the longest in prayer and the most frequent in fasting. But when they leave the bridge behind them, they shed blood and seize wealth." He said: "You will be asked about them only this. I told them: 'Do not kill Sayyiduna Uthman (may Allah be pleased with him); leave him alone. By Allah, if you leave him for eleven nights, he will die in his bed.' But they did not do so. When any prophet is killed, seventy thousand people are killed in retaliation for him, and when any caliph is killed, thirty-five thousand people are killed in retaliation for him."