Whenever I tell you a narration from Messenger of Allah ﷺ, by Allah, I would rather fall down from the sky than ascribe a false statement to him, but if I tell you something between me and you (not a Hadith) then it was indeed a trick (i.e., I may say things just to cheat my enemy). No doubt I heard Allah's Apostle saying, "During the last days there will appear some young foolish people who will say the best words but their faith will not go beyond their throats (i.e. they will have no faith) and will go out from (leave) their religion as an arrow goes out of the game. So, where-ever you find them, kill them, for who-ever kills them shall have reward on the Day of Resurrection."  

عَلِيٌّ ؓ إِذَا حَدَّثْتُكُمْ عَنْ رَسُولِ اللَّهِ ﷺ حَدِيثًا فَوَاللَّهِ لأَنْ أَخِرَّ مِنَ السَّمَاءِ أَحَبُّ إِلَىَّ مِنْ أَنْ أَكْذِبَ عَلَيْهِ وَإِذَا حَدَّثْتُكُمْ فِيمَا بَيْنِي وَبَيْنَكُمْ فَإِنَّ الْحَرْبَ خَدْعَةٌ وَإِنِّي سَمِعْتُ رَسُولَ اللَّهِ ﷺ يَقُولُ سَيَخْرُجُ قَوْمٌ فِي آخِرِ الزَّمَانِ حُدَّاثُ الأَسْنَانِ سُفَهَاءُ الأَحْلاَمِ يَقُولُونَ مِنْ خَيْرِ قَوْلِ الْبَرِيَّةِ لاَ يُجَاوِزُ إِيمَانُهُمْ حَنَاجِرَهُمْ يَمْرُقُونَ مِنَ الدِّينِ كَمَا يَمْرُقُ السَّهْمُ مِنَ الرَّمِيَّةِ فَأَيْنَمَا لَقِيتُمُوهُمْ فَاقْتُلُوهُمْ فَإِنَّ فِي قَتْلِهِمْ أَجْرًا لِمَنْ قَتَلَهُمْ يَوْمَ الْقِيَامَةِ  

That they visited Abu Saʿid Al-Khudri and asked him about Al-Harauriyya, a special unorthodox religious sect, "Did you hear the Prophet ﷺ saying anything about them?" Abu Saʿid said, "I do not know what Al-Harauriyya is, but I heard the Prophet ﷺ saying, "There will appear in this nation---- he did not say: From this nation ---- a group of people so pious apparently that you will consider your prayers inferior to their prayers, but they will recite the Qur'an, the teachings of which will not go beyond their throats and will go out of their religion as an arrow darts through the game, whereupon the archer may look at his arrow, its Nasl at its Risaf and its Fuqa to see whether it is blood-stained or not (i.e. they will have not even a trace of Islam in them).  

أَسَمِعْتَ النَّبِيَّ ﷺ قَالَ لاَ أَدْرِي مَا الْحَرُورِيَّةُ سَمِعْتُ النَّبِيَّ ﷺ يَقُولُ يَخْرُجُ فِي هَذِهِ الأُمَّةِ وَلَمْ يَقُلْ مِنْهَا قَوْمٌ تَحْقِرُونَ صَلاَتَكُمْ مَعَ صَلاَتِهِمْ يَقْرَءُونَ الْقُرْآنَ لاَ يُجَاوِزُ حُلُوقَهُمْ أَوْ حَنَاجِرَهُمْ يَمْرُقُونَ مِنَ الدِّينِ مُرُوقَ السَّهْمِ مِنَ الرَّمِيَّةِ فَيَنْظُرُ الرَّامِي إِلَى سَهْمِهِ إِلَى نَصْلِهِ إِلَى رِصَافِهِ فَيَتَمَارَى فِي الْفُوقَةِ هَلْ عَلِقَ بِهَا مِنَ الدَّمِ شَىْءٌ  

Regarding Al-Harauriyya: The Prophet ﷺ said, "They will go out of Islam as an arrow darts out of the game's body.'  

قَالَ النَّبِيُّ ﷺ يَمْرُقُونَ مِنَ الإِسْلاَمِ مُرُوقَ السَّهْمِ مِنَ الرَّمِيَّةِ