Allâh's Messenger (ﷺ) said, "The bartering of gold for gold, is Riba, (usury), except if it is from hand to hand and equal in amount, and wheat grain for wheat grain is Riba (usury) except if it is from hand to hand and equal in amount, and dates for dates is Riba (usury) except if it is from hand to hand and equal in amount, and barley for barley is Riba (usury) except if it is from hand to hand and equal in amount. [3:344-O.B]