Musnad Abu Ya'la al-Mawsili 42:244

Zuhayr narrated to us, Abd al-Samad narrated to us, Shu'bah narrated to us, Abdullah al-Za'farani narrated to us, from Abu al-Mutawakkil al-Naji, from Abu Sa'id, who said: The Messenger of Allah (may Allah bless him and grant him peace) said: "Silver for silver, and gold for gold, equal for equal, like for like. Whoever increases or seeks an increase has committed usury (riba), and the taker and the giver are the same."