Musnad Ahmad 30:1246

Abu Bakr al-Hanafi narrated to us, al-Dahhak bin Uthman narrated to us, Bukayr bin Abdullah bin al-Ashajj narrated to me, from Sulayman bin Yasar, that the merchants' vouchers (sakkak) were issued. The merchants sought permission from Marwan to sell them, and he permitted them. Abu Hurayrah entered upon him and said to him: "You have permitted the sale of usury (riba), while the Messenger of Allah, may Allah bless him and grant him peace, has forbidden that food be purchased and then sold until it is taken possession of." Sulayman said: "I saw Marwan send the guards, and they began to snatch the vouchers from the hands of those who did not feel constrained by it."