The hadith
The Prophet ﷺ said: "Gold for gold, silver for silver, wheat for wheat, barley for barley, dates for dates, salt for salt — like for like, equal for equal, hand to hand. If the genus differs, then sell as you wish, but only hand to hand." (Sahih Muslim 1587, Sahih Bukhari 2178)
This hadith is the foundational text for the entire bai' al-sarf framework in classical and modern fiqh. The six commodities — gold, silver, wheat, barley, dates, salt — became the canonical examples of "ribawi items" (الأصناف الربوية), and classical jurists generalised the principles to derive the rules for any exchange of monetary or measurable-fungible assets.
The two principles derived
- Same genus, same quantity: when exchanging like-for-like (gold for gold, USD for USD), quantities must be equal. Asymmetric exchange = riba al-fadl.
- Different genus, same session: when exchanging different-genus items (gold for silver, USD for EUR, fiat for crypto), the quantities can differ — but both sides must take possession in the same session. Deferred = riba al-nasi'ah.
Why the genus generalisation matters for crypto
Classical jurists were emphatic that the principles applied to "anything with similar characteristics" — anything that functions as a measurable, fungible, monetary, or quasi-monetary asset. The six items are illustrative, not exhaustive.
For crypto:
- Bitcoin for Bitcoin (e.g., wrapping/unwrapping)? Same-genus rule applies — must be equal in quantity, immediate.
- Bitcoin for ETH? Different-genus, so quantity can differ — but immediate (taqabudh) is required.
- Bitcoin for fiat? Different-genus monetary exchange — bai' al-sarf rules in full force.
This is the structural reason crypto futures and perpetuals fail the test: deferring delivery in a different-genus monetary exchange violates the "hand to hand" requirement that the hadith makes explicit.
What the hadith does NOT prohibit
The hadith does not prohibit exchange itself — exchange is encouraged. It prohibits specific structures of exchange:
- Unequal exchange of the same genus
- Deferred exchange of any monetary asset
A spot trade of BTC for USDT on a regulated exchange satisfies both conditions: different genus, same-session settlement. This is why halal crypto trading is structurally compatible with the ribawi-items principles, while leveraged derivatives are not.
Stablecoin caution
The ribawi-items analysis becomes stricter when the quote asset is a stablecoin. A same-session BTC/USDT trade may satisfy the exchange mechanics, but the stablecoin itself still needs screening for reserve composition, redemption rights, and interest exposure. A launch-ready halal universe should not assume that every dollar token is interchangeable. It should prefer screened quote assets, disclose the basis for their inclusion, and exclude any stablecoin whose yield or reserve structure creates avoidable riba exposure.