Musannaf Ibn Abi Shayba 38:134

'Amr ibn Yahya ibn 'Amr ibn Salamah narrated to us, from his father, from his grandfather, who said: We were sitting at the door of 'Abdullah, waiting for him to come out to us. He came out and said: "The Messenger of Allah (may Allah bless him and grant him peace) told us that there are people who recite the Qur'an, but it does not go beyond their collarbones. They pass through Islam just as an arrow passes through the game." And by Allah, I do not know, perhaps most of them are from among you. 'Amr ibn Salamah said: So we saw most of those people fighting against us on the day of Nahrawan with the Khawarij.