Musnad Abu Ya'la al-Mawsili 108:151

Zuhayr narrated to us, 'Abbad ibn al-'Awwam narrated to us, from Sufyan ibn Husayn, from Yunus ibn 'Ubayd, from 'Ata', from Jabir: That the Prophet (peace and blessings of Allah be upon him) forbade the *thunya* (exception in a sale), unless it is known.