Sahih Bukhari | Volume 4 | Hadith Number 808
Narrated by 'Ali
I relate the traditions of Allah's Apostle to you for I would rather fall from the sky than attribute something to him falsely. But when I tell you a thing which is between you and me, then no doubt, war is guile. I heard Allah's Apostle saying, "In the last days of this world there will appear some young foolish people who will use (in their claim) the best speech of all people (i.e. the Qur'an) and they will abandon Islam as an arrow going through the game. Their belief will not go beyond their throats (i.e. they will have practically no belief), so wherever you meet them, kill them, for he who kills them shall get a reward on the Day of Resurrection."