‘Ubada b. as-Samit reported God's Messenger as saying, "Gold is to be paid for by gold, silver by silver, wheat by wheat, barley by barley, dates by dates, and salt by salt, like for like and equal for equal, payment being made on the spot. If these classes differ, sell as you wish if payment is made on the spot.” Muslim transmitted it.
The Prohibition of Riba in Exchange Transactions
This noble hadith from Sahih Muslim establishes the foundational principles governing the exchange of specific commodities known as "ribawi items." The Messenger of Allah ﷺ explicitly mentions six commodities: gold, silver, wheat, barley, dates, and salt. These represent categories of items that share the same underlying cause ('illah) for the ruling.
Conditions for Same-Category Exchanges
When exchanging gold for gold, or any item within the same category, two strict conditions apply: the exchange must be "like for like" (equal in weight for items measured by weight, or equal in volume for items measured by volume), and the transaction must be completed immediately with no delay in payment (hand-to-hand).
This prohibition prevents the subtle forms of usury (riba) that can occur when there is inequality in quantity or delay in payment, which effectively constitutes interest.
Cross-Category Exchange Rules
When exchanging items from different categories (such as gold for silver, or wheat for dates), the requirement for equality in measurement is lifted. However, the condition of immediate payment remains absolutely essential. The transaction must be completed on the spot without any deferment of either commodity.
Contemporary Application
Modern scholars have extended these principles to contemporary currencies and commodities. Paper currency falls under the ruling of gold and silver, requiring immediate exchange at the prevailing rate when trading different currencies. The wisdom behind these regulations is to ensure justice in transactions and prevent exploitation through hidden interest.