Musnad Abu Ya'la al-Mawsili 78:3

Zuhayr ibn Harb narrated to us, Isma'il ibn Ibrahim narrated to us, Ayyub narrated to us, from Abu Qilabah, who said: People used to buy gold with silver on credit. Isma'il said: I think he said "until the time of the stipend." Then Hisham ibn 'Amir came upon them and forbade them, and said: "Indeed, the Messenger of Allah (ﷺ) forbade that we sell gold with silver on credit." And he informed us—or he said: he told us—that that is usury (riba).