Gold is to be paid for by gold with equal weight, like for like, and silver is to be paid for by silver with equal weight, like for like. He who made an addition to it or demanded an addition dealt in usury.
The Book of Musaqah - Sahih Muslim 1588 c
This narration from the Prophet Muhammad (peace be upon him) establishes the fundamental Islamic prohibition against riba (usury/interest) in gold and silver transactions, which serve as the basis for currency regulations in Islamic economics.
Scholarly Commentary
The requirement of equal weight for gold-to-gold and silver-to-silver exchanges prevents any form of excess or deficiency that would constitute usury. This ruling applies regardless of whether the items are in coin form, raw bullion, or manufactured jewelry.
The prohibition encompasses both giving and receiving excess - "he who made an addition or demanded an addition" - making both parties equally responsible for avoiding usurious transactions. This strict equality requirement eliminates any time-based advantage or quality differential that could disguise interest.
Legal Implications
This hadith forms the foundation for the classical Islamic rules of sarf (currency exchange), requiring immediate exchange and equal weight when trading gold for gold or silver for silver. Any delay in exchange or difference in quantity invalidates the transaction.
Modern scholars extend this principle to paper currency and digital money, requiring spot exchange at equal face value when trading the same currency, while allowing differential rates only when exchanging different currencies with immediate settlement.
Wisdom Behind the Prohibition
This ruling protects society from economic exploitation and ensures fairness in monetary transactions. By eliminating hidden interest in currency exchanges, it maintains the stability of the monetary system and prevents wealth concentration through unjust means.
The prohibition encourages productive economic activity rather than wealth generation through mere monetary manipulation, aligning with Islam's emphasis on justice and equitable distribution of resources.