When the Khawarij rebelled and fought in An-Nahrawan, ‘Ali (رضي الله عنه) stood before his companions and said: These people have shed blood that it is forbidden to shed and have raided the flocks of the people. They are the closest of the enemy to you, but if you go to your enemy, I am afraid that these people may attack what you leave behind. I heard the Messenger of Allah (ﷺ) say: "Some rebels will emerge from my ummah, your prayer will be as nothing compared to their prayer, and your fasting will be as nothing compared to their fasting, and your recitation will be as nothing compared to their recitation. They will recite the Qur"an, thinking that it is in their favour, but it will be against them; it will go no further than their throats. They will pass out of Islam as the arrow passes out of the prey. The sign of that is that among them will be a man who has an upper arm but no forearm, and on it will be something like the nipple of a breast, on which will be some white hairs." If the army that fights them knew what reward they will have, as spoken on the lips of their Prophet (ﷺ), they would cease striving and rely on that. March forth in the Name of Allah. And he narrated the hadeeth at length.