From Sahih Bukhari (Hadith 6934):
Narrated Yusair bin `Amr:I asked Sahl bin Hunaif, "Did you hear the Prophet (ﷺ) saying anything about Al-Khawarij?" He said, "I heard him saying while pointing his hand towards Iraq. "There will appear in it (i.e, Iraq) some people who will recite the Qur'an but it will not go beyond their throats, and they will go out from (leave) Islam as an arrow darts through the game's body
Reference: Bukhari 6934