in .) However, M.A. Khan argues, "the Prophet could easily have announced the broad features of such a law [against Riba]. The fact is that neither the Prophet nor the Qur'an has announced any law relating to interest", as they had "in the case of theft, adultery or murder. .... Neither the Prophet nor the first four caliphs nor any subsequent Islamic government ever enacted any law against riba." Attempts to do so are "quite recent". The "authentic books of Islamic jurisprudence (fiqh) produced throughout Islamic history" had "sections dealing with riba", discussing "its nature and what makes a transaction lawful or unlawful", but according to M.A. Khan, until recently none contained "any public law for enforcement through state machinery." The treasure of Islamic jurisprudence which has covered all facets of life, including imaginary situations, does not mention any punishment for one who indulges in riba." In 1999 a work did. The Blueprint of Islamic financial system including strategy for elimination of Riba by the International Institute of Islamic Economics, called for riba-based transactions to be punishable by law. Another (non-Muslim) scholar (Olivier Roy) points out Ayatollah Ruhollah Khomeini's book of fatawa Tawzih al-masa'il, written before 1962, as an example of a more traditionalist attitude toward riba, or at least the charging of interest on loans. Rather than calling for a ban on interest, Khomeini states that lending without charging interest, "is among the good works" (Mustahabb) that are "particularly recommended in the verses of the Quran and in the Hadiths." Scriptural proof and fiqh According to Farhad Nomani while classical jurists had "a consensus of opinion about the prohibition of riba", they disagreed on the "interpretation of the primary Islamic sources and, consequently, over the details of the ruling on riba". They believed that the "objects of riba occur in sale, and, only by analogy they related riba to loan ..." Madhhab (schools of fiqh), differ somewhat in their interpretation of riba. The Shafi'i hold that injunctions for riba apply to gold and silver currency but not fils (non-precious metal currency). "Thus, one hundred fils [coins made of neither silver or gold] could be exchanged for two hundred either on the spot or on a deferred delivery basis." By extension this would apply to contemporary fiat [i.e. paper] money, according to Abdullah Saeed. (One author — Imad-ad-Dean Ahmad — argues "ribâ as it is used in the Qur'an and