Any kind of wealth or property (mal) that is inherently susceptible to riba. Traditionally, al-amwal al-ribawiyah (plural of al-mal al-ribawi) refer to any of the six substances (items) that are sold by weight and measure, literally: gold, silver, dates, wheat, salt and barley. Exchanging these substances in kind must be in equal measure and with immediate transfer of possession (qabdh) in order to avoid exchanging unequal amounts (measures and weights) or the so called riba in trade (riba al-fadhl). If carried out in conformity to these conditions, then the exchange is riba-free (i.e., halal/ permissible/ shari’a compliant).

Riba al-fadhl arises in transactions where ribawi items of the same kind are exchanged in different measures or weights, even if the exchanged amounts differ in quality. Gold and silver are generally classified as mal ribawi and so are present day fiat money based on qiyas.