Musnad Abu Ya'la al-Mawsili 42:315

Zuhayr narrated to us, Abu al-Walid Hisham ibn Abd al-Malik narrated to us, Hammam narrated to us, Zayd ibn Aslam narrated to us, from Ata ibn Yasar, from Abu Sa’id al-Khudri, from the Prophet (peace be upon him), who said: "Do not write anything from me other than the Quran. Whoever has written anything from me other than the Quran, let him erase it."