Usury

RIB$ (a.), lit. increase, as a technical term,
usury and interest
usury and interest, and in general any unjustified increase of capital for which no compensation is given. Derivatives from the same root are used in other Semitic languages to describe interest.

A. In classical Islamic law.

1. Transactions with a fixed time limit and payment of interest, as well as speculations of all kinds, formed an essential element in the highly developed trading system of Mecca (cf. Lammens, La Mecque à la veille de l'hégire, 139 ff., 155 ff., 213-14). Among the details given by the Muslim sources we may believe at least the statement that a debtor who could not repay the capital (money or goods) with the accumulated interest at the time it fell due, was given an extension of time in which to pay, but at the same time the sum due was doubled. This is clearly referred to in two passages in the ur"§n (III, 130; XXX, 39) and is in keeping with a still usual practice. As early as såra XXX, 39, of the third Meccan period (on the dating, cf. Nöldeke-Schwally, Geschichte des Qor§ns, i), the ur"§n contrasts rib§with the obligation to pay zak§tbut without directly forbidding it: “Whatever ye give in usury to gain interest from men's substance shall not bear interest with All§h, but what ye give as zak§tin seeking the face of All§h, these shall gain double”. The express prohibition follows in III, 130 (Medinan, [VIII:491b] obviously earlier than the following passage): “Believers, devour not the rib§with continual doubling; fear God, perhaps it will go with you”. This prohibition had to be intensified in II, 275-80 (evidently of the earlier Medinan period, cf. the following passage): “Those who devour rib§shall only rise again as one whom Satan strikes with his touch; this because they say, 'selling is like usury'; but All§h has permitted selling and forbidden usury.

(Quoted from Encyclopaedia of Islam, Brill Publishers)