Hiring/Renting: The Property by Which Rent is Paid
Practical Laws of Islam as per the teachings of Ayatullah Sistani
Ruling 2203
The property by which the lessee pays rent must be known. Therefore, if the property is something that is transacted by weight, such as wheat, then its weight must be known. If it is something that is transacted by count, such as modern currencies, its count must be known. And if it is something like horses and sheep, the lessor must see them for himself or the lessee must describe their particulars to him.
-Ayatullah Sistani, Practical Laws of Islam, Hiring/Renting (Ijarah)