They previously connected their position on "zakat" with promotion of the Islamic gold dinar and silver dirham, which was developed above all by the scholar Umar Ibrahim Vadillo. Paper money, since actually a promise of payment written on paper, can from the point of view of "zakat" only be considered in terms of its value as paper, since "zakat" cannot be discharged by passing on a token of debt owed to a third party. Vadillo has written extensively on the origins of paper money and the Islamic position on money.