When the Khawarij rebelled and fought in An-Nahrawan, ‘Ali ؓ 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: ʿSome 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 Qurʿan, 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.ʿ 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.  

لَمَّا خَرَجَتِ الْخَوَارِجُ بِالنَّهْرَوَانِ قَامَ عَلِيٌّ فِي أَصْحَابِهِ فَقَالَ إِنَّ هَؤُلَاءِ الْقَوْمَ قَدْ سَفَكُوا الدَّمَ الْحَرَامَ وَأَغَارُوا فِي سَرْحِ النَّاسِ وَهُمْ أَقْرَبُالْعَدُوِّ إِلَيْكُمْ وَأَنْ تَسِيرُوا إِلَى عَدُوِّكُمْ أَنَا أَخَافُ أَنْ يَخْلُفَكُمْ هَؤُلَاءِ فِي أَعْقَابِكُمْ إِنِّي سَمِعْتُ رَسُولَ اللهِ ﷺ يَقُولُ تَخْرُجُ خَارِجَةٌ مِنْ أُمَّتِي لَيْسَ صَلَاتُكُمْ إِلَى صَلَاتِهِمْ بِشَيْءٍ وَلَا صِيَامُكُمْ إِلَى صِيَامِهِمْ بِشَيْءٍ وَلَا قِرَاءَتُكُمْ إِلَى قِرَاءَتِهِمْ بِشَيْءٍ يَقْرَءُونَ الْقُرْآنَ يَحْسِبُونَ أَنَّهُ لَهُمْ وَهُوَ عَلَيْهِمْ لَا يُجَاوِزُ حَنَاجِرَهُمْ يَمْرُقُونَ مِنَ الْإِسْلَامِ كَمَا يَمْرُقُ السَّهْمُ مِنَ الرَّمِيَّةِ وَآيَةُ ذَلِكَ أَنَّ فِيهِمْ رَجُلًا لَهُ عَضُدٌ وَلَيْسَ لَهَا ذِرَاعٌ عَلَيْهَا مِثْلُ حَلَمَةِ الثَّدْيِ عَلَيْهَا شَعَرَاتٌ بِيضٌ لَوْ يَعْلَمُ الْجَيْشُ الَّذِينَ يُصِيبُونَهُمْ مَا لَهُمْ عَلَى لِسَانِ نَبِيِّهِمْ لاتَّكَلُوا عَلَى الْعَمَلِ فَسِيرُوا عَلَى اسْمِ اللهِ فَذَكَرَ الْحَدِيثَ بِطُولِهِ