It is narrated from Umar bin Khattab (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "The sale of gold for silver, if not done on the spot, is usury; the sale of grain for grain, if not done on the spot, is usury; the sale of dates for dates, if not done on the spot, is usury; and the sale of barley for barley, if not done on the spot, is usury."
Hadith Referenceمسند الإمام الشافعي / كتاب البيوع / 1393
Hadith Takhrijانظر الحديث السابق برقم (1391 ، 1392)۔