Musnad Ahmad 31:771

Ya'qub narrated to us, my father narrated to us, from Ibn Ishaq, Yazid ibn 'Abd Allah ibn Qusayt narrated to me, that Abu Salamah and Muhammad ibn 'Abd al-Rahman ibn Thawban informed him that they heard Abu Sa'id al-Khudri narrating that the Messenger of Allah (may Allah bless him and grant him peace) distributed among them food of different kinds, some of which was better than others. He said: So we went to increase [the value] among ourselves, but the Messenger of Allah (may Allah bless him and grant him peace) forbade us from trading it except measure for measure, with no increase in it.