Sahih Muslim
The Book of Zakat (Kitab Al-Zakat)
Book Number: 005 / Hadith Number: 2336
Yusair b. 'Amr reported that he inquired of Sahl b. Hunaif: Did you hear the Apostle of Allah (may peace be upon him) making a mention of the Khwarij? He said: I heard him say (and he pointed with his hand towards the east) that these would be a people who would recite the Qur'an with their tongues and it would not go beyond their collar bones. They would pass clean through their religion just as the arrow passes through the prey.