فإذا بيع المكيل أو الموزون بجنسه مثلا بمثل جاز البيع وإن تفاضلا لم يجز
Translation: A measured or weighed commodity may be sold for an equal amount of its own genus; an unequal exchange is not permissible.
An exchange of one ribawi genus like for like satisfies the quantity requirement. This does not mean that deferment is thereby allowed: where both operative attributes coincide, delay is separately prohibited.
Thus 5 saʿ of dates against 5 saʿ of the same genus, immediately exchanged, passes the equality test. Delivering one side today and scheduling the identical quantity next month does not pass the deferment test.