Is it permissible to conduct a Salam contract using one type of measureable good for another, such as exchanging a unit of weight for a unit of measure?
Chapter on Guaranteed Salaf (Advance Payment) for a Specified Term
Al-Mughni
Book of Sales
Primary text
It is not permissible to enter into a Salam contract exchanging a good defined by weight for one defined by measure, or vice versa. This conclusion aligns with the apparent view of Ahmad, who expressed disapproval when asked about this matter. Consequently, the subject of the Salam contract cannot be currency. This is the position of Abu Hanifa, as currency is established in the debt only as a price (*thaman*), and thus cannot be the priced object (*muthman*).
Supporting text
According to the narration that permits deferred exchange in commodities, the capital of the Salam can be a commodity, just like the price, and commodities can be contracted for in exchange for currency. This view supports the permissibility of Salam in gold and silver, following Malik and Al-Shafi'i.