It is narrated from Uthman Shahham, he says: Muslim bin Abi Bakrah narrated to us that he asked him whether he had heard any hadith regarding the Khawarij? He said: I heard my father, Sayyiduna Abu Bakrah (may Allah be pleased with him), say that the Noble Prophet (peace and blessings be upon him) said: Beware! Soon there will arise from my Ummah people who will be harsh and severe in religious matters, their tongues will be very skilled with the Qur'an, but it will not go below their collarbones. When you see them, kill them. Then I say again, when you see them, kill them. The one who kills them will be deserving of reward.