كتاب الزكاة
12
The Book of Zakat
(48)
Chapter: Exhortation to kill the Khawarij
(48)
باب التَّحْرِيضِ عَلَى قَتْلِ الْخَوَارِجِ ‏

'Ali said:

Whenever I narrate to you anything from the Messenger of Allah (ﷺ) believe it to be absolutely true as falling from the sky is dearer to me than that of attributing anything to him (the Holy Prophet) which he never said. When I talk to you of anything which is between me and you (there might creep some error in it) for battle is an outwitting. I heard the Messenger of Allah (ﷺ) as saying: There would arise at the end of the age a people who would be young in age and immature in thought, but they would talk (in such a manner) as if their words are the best among the creatures. They would recite the Qur'an, but it would not go beyond their throats, and they would pass through the religion as an arrow goes through the prey. So when you meet them, kill them, for in their killing you would get a reward with Allah on the Day of Judgement.
حَدَّثَنَا مُحَمَّدُ بْنُ عَبْدِ اللَّهِ بْنِ نُمَيْرٍ، وَعَبْدُ اللَّهِ بْنُ سَعِيدٍ الأَشَجُّ، جَمِيعًا عَنْ وَكِيعٍ، - قَالَ الأَشَجُّ حَدَّثَنَا وَكِيعٌ، - حَدَّثَنَا الأَعْمَشُ، عَنْ خَيْثَمَةَ، عَنْ سُوَيْدِ بْنِ غَفَلَةَ، قَالَ قَالَ عَلِيٌّ إِذَا حَدَّثْتُكُمْ عَنْ رَسُولِ اللَّهِ صلى الله عليه وسلم فَلأَنْ أَخِرَّ مِنَ السَّمَاءِ أَحَبُّ إِلَىَّ مِنْ أَنْ أَقُولَ عَلَيْهِ مَا لَمْ يَقُلْ وَإِذَا حَدَّثْتُكُمْ فِيمَا بَيْنِي وَبَيْنَكُمْ فَإِنَّ الْحَرْبَ خَدْعَةٌ ‏.‏ سَمِعْتُ رَسُولَ اللَّهِ صلى الله عليه وسلم يَقُولُ ‏ "‏ سَيَخْرُجُ فِي آخِرِ الزَّمَانِ قَوْمٌ أَحْدَاثُ الأَسْنَانِ سُفَهَاءُ الأَحْلاَمِ يَقُولُونَ مِنْ خَيْرِ قَوْلِ الْبَرِيَّةِ يَقْرَءُونَ الْقُرْآنَ لاَ يُجَاوِزُ حَنَاجِرَهُمْ يَمْرُقُونَ مِنَ الدِّينِ كَمَا يَمْرُقُ السَّهْمُ مِنَ الرَّمِيَّةِ فَإِذَا لَقِيتُمُوهُمْ فَاقْتُلُوهُمْ فَإِنَّ فِي قَتْلِهِمْ أَجْرًا لِمَنْ قَتَلَهُمْ عِنْدَ اللَّهِ يَوْمَ الْقِيَامَةِ ‏"‏ ‏.‏
Reference : Sahih Muslim 1066 a
In-book reference : Book 12, Hadith 199
USC-MSA web (English) reference : Book 5, Hadith 2328
  (deprecated numbering scheme)