Sunan an-Nasa'i, Book 37, Hadith 137 (In-Book) ⓘ

It was narrated that 'Ali said: "I heard the Messenger of Allah [SAW] say: 'At the end of time there will appear young people with foolish minds. Their faith will not pass through their throats, and they will go out of Islam as an arrow goes through the target. If you meet them, then kill them, for killing them will bring reward to the one who killed them on the Day of Resurrection.'"

أَخْبَرَنَا مُحَمَّدُ بْنُ بَشَّارٍ، قَالَ حَدَّثَنَا عَبْدُ الرَّحْمَنِ، قَالَ حَدَّثَنَا سُفْيَانُ، عَنِ الأَعْمَشِ، عَنْ خَيْثَمَةَ، عَنْ سُوَيْدِ بْنِ غَفَلَةَ، عَنْ عَلِيٍّ، قَالَ سَمِعْتُ رَسُولَ اللَّهِ صلى الله عليه وسلم يَقُولُ ‏ "‏ يَخْرُجُ قَوْمٌ فِي آخِرِ الزَّمَانِ أَحْدَاثُ الأَسْنَانِ سُفَهَاءُ الأَحْلاَمِ يَقُولُونَ مِنْ خَيْرِ قَوْلِ الْبَرِيَّةِ لاَ يُجَاوِزُ إِيمَانُهُمْ حَنَاجِرَهُمْ يَمْرُقُونَ مِنَ الدِّينِ كَمَا يَمْرُقُ السَّهْمُ مِنَ الرَّمِيَّةِ فَإِذَا لَقِيتُمُوهُمْ فَاقْتُلُوهُمْ فَإِنَّ قَتْلَهُمْ أَجْرٌ لِمَنْ قَتَلَهُمْ يَوْمَ الْقِيَامَةِ ‏" ‏ ‏.‏