Musnad Abu Ya'la al-Mawsili 152:329

Ishaq ibn Ibrahim Abu Musa al-Harawi narrated to us, al-Nadr ibn Shumayl narrated to us, Yunus ibn Abi Ishaq narrated to us, from his father, from Abu al-Ahwas, from Abdullah, who said: The people used to recite aloud behind the Messenger of Allah, may Allah bless him and grant him peace. So the Messenger of Allah, may Allah bless him and grant him peace, said to them: "You have confused the Qur'an for me."