days of Jahiliyya", he makes no mention of debts being doubled, but states that riba "had different forms" and that "the common feature of all these transactions is that an increased amount was charged on the principal amount of a debt." Riba According to orthodox sources (Youssouf Fofanaa, Taqi Usmani), "some jurists" saw riba (which Fofanaa defines as interest) "forbidden early in Mecca, some in the year 2 AH (after Muhammad left Mecca for Medina), and some after the opening of Mecca, but the majority agreed on its prohibition". Usmani cites sources declaring that 3:129 "clearly" forbade interest and these verses were revealed in 2 AH. Other sources — such as the Encyclopedia of Islam and the Muslim World — state that early Muslims disagreed on whether all or only exorbitant rates of interest could be considered riba, and thus declared forbidden, but the broader definition won out with a consensus of Muslim jurists holding that any loan that involved an increase in repayments was forbidden. One particular jurist (al-Jassas, d.981, who is criticized by Modernists) is credited with establishing the orthodox definition of riba — stipulating that it was excess payment "in a loan or debt", (i.e. interest on debt). M. A. Khan argues that attempts to ban interest resulted in either the development of black markets and higher prices for "interest-bearing credit", which "defeat[ed] the very purpose for which interest was banned"; or in various "subterfuges to camouflage interest so as to bypass the legal sanctions". Some (scholar Timur Kuran) attribute the basis of religious condemnation of interest on loans to the widespread practice in the ancient world of selling loan defaulters into slavery and shipping them to foreign lands. Feisal Khan argues that "all pre-modern, and not just Muslim societies" banned interest on loans, using a ban as "a simple and effective risk-mitigation mechanism for small borrowers that cannot afford the down-side risk inherent in financial transactions". Among other monotheist Abrahamic religions, Christian theologians condemned interest as an "instrument of avarice", the Jewish Torah prohibited lending at interest to fellow Jews but allowed it to non-Jews (i.e. Gentiles) (Deut. 23:20). (Historically many Jews were led to money lending with interest as a profession because of this exemption and because they were barred from many professions in Christian territories.) With modernity and economic development, higher incomes and more complex mechanisms such as insurance eliminated the need for the