—may Allah bless him and grant him peace—and whatever has no recognized measure or weight in those two cities is assessed according to the custom of its own locality.

Section
Deferred usury (ribā al-nasīʾah) is forbidden in every sale of two commodities that share the effective cause of incremental usury (ribā al-faḍl) when neither of them is a currency, such as two items sold by measure or two sold by weight; and if the parties separate before taking possession, the transaction is void.

If a measured commodity is exchanged for a weighed one, separation before delivery and deferment of payment are both permissible. With items that are neither measured nor weighed—such as cloth and livestock—deferment is likewise allowed.

The sale of one debt for another is invalid.

Section
Whenever the two parties to a currency exchange separate before full or partial possession has been taken, the contract is void with respect to whatever has not been received.

Dirhams and dinars become specified once they are named in the contract and may not be substituted. If the coins are later found to be usurped property, the contract is null; if they are defective yet of the same kind, the buyer may either keep them or return them.

Usury is forbidden between a Muslim and a belligerent non-Muslim, and categorically forbidden among Muslims.1

Chapter on the Sale of Real Property and Produce
When a house is sold, the sale includes its land, its structure, its roof, the fixed door,2 the staircase, the nailed-down shelf, and any buried storage jar—but not the goods deposited inside that jar.