E. View of the school of law on the underlying cause of the prohibition of the six ribawi items

In addition to the six ribawi items mentioned in the Hadith, Shariah scholars included other types of commodities depending on the underlying cause specified. This extension of Shariah ruling is done by referring to the analogy as source of law. Qiyas is the extension of a Shariah rule from the original case, or asl, to a new case, because the latter has the same effective cause (‘illah) as the former. Hence, when the illah is found in another commodity, the Shariah ruling will be extended accordingly.  Scholars agreed on the underlying cause of (gold and silver) which is currency, however the scholars have different views in identifying the illah in the four commodities. The different opinions are as the table.