Religious observance and market law in medieval Islam: The controversal application of the prohibition of usury according to some Ibâḍî sources

Especially on the prohibition of Ribā. Pp. 200-201: in dealing with the Ribā prohibition, one can point out a further incongruity in the Ibāḍī law. As stated above, money exchange and, in general, dealings in precious metals demanded immediate delivery of the two lots which had been exchanged. This doctrine was generally accepted but, among the Ibāḍīs, the ʿUmānī scholar Ibn Baraka (middle of the 5th/11th c.) stated that the exchange of gold for silver on credit is allowed. ... The doctrine of Ibn Baraka did not become part of the school’s teaching. This doctrine may be regarded as a survival of the original Medinese custom in that some traditions quoted by Muslim reported that, during the Prophet’s lifetime, people in Medina used to exchange gold for silver on credit.