be any such excess. A difference in quantity is therefore permissible.

The second rationale:

This is the rationale of those who hold that a commodity subject to the rules of riba may be exchanged for another such commodity on the basis of careful appraisal and estimation when there is a need and measurement by volume or weight is not possible. Mālik, al-Shāfi‘ī and Ahmad hold this view concerning ‘arāyā sales based on estimation, in accordance with the Sunnah permitting fresh dates to be exchanged for dried dates on an estimated basis because of need. According to one view within the school of Ahmad and elsewhere, this is permissible for all fruits. According to a second view, it is not permissible; according to a third, it is permissible only for grapes and fresh dates, as some of al-Shāfi‘ī’s followers also hold.

Similarly, Mālik and his followers permit goods normally sold by weight to be exchanged on the basis of careful appraisal when there is a need. Thus, they permit bread to be exchanged for bread on this basis, and they also permit meat to be exchanged for meat on this basis while travelling.

They argued that the need arises when people have no scales, so this is permissible just as ‘arāyā sales are permissible. They distinguished this from measurement by volume, since that remains possible even by using handfuls.

Since the Sunnah has established that careful appraisal and considered judgment may take the place of certain knowledge obtained by measuring or weighing when there is a need, it is well known that people need to exchange these debased dirhams for these pure ones, and they have ascertained the amount of silver they contain