on a deferred basis, whatever the commodity, whether food or otherwise. As for exchanges between two different kinds, it applies to two categories: the first is gold and silver; the second is all food, whether or not it can be stored.
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Currency exchange is among the most tightly restricted areas relating to usury. Avoiding usury is difficult for anyone whose trade is currency exchange, except those who are scrupulous and know what is lawful and unlawful in it—and how few they are. Hence al-Hasan used to say: “If you ask for water and are served water from a money changer’s house, do not drink it.” Asbagh disliked even seeking shade at a money changer’s premises. Ibn Habīb said: “Because usury predominates in their dealings.” Mālik—may Allah Most High have mercy on him—was asked: “Do you disapprove of a man working in currency exchange?” He replied: “Yes, unless he fears Allah in conducting it.”
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Among the forms of usury that the Prophet (peace and blessings be upon him) clarified is that gold may be sold for gold, and silver for silver, only in equal amounts and hand to hand, while gold may be sold for silver only hand to hand. Mālik (may Allah have mercy on him) related in his Muwatta’, from Ibn Shihāb, from Mālik ibn Aws ibn al-Hadathān al-Nasrī, that he sought to exchange one hundred dinars. He said:
“Talhah ibn ‘Ubayd Allāh called me over, and we negotiated until he concluded an exchange with me. He took the gold and turned it over in his hand, then said: ‘Wait until my treasurer comes from al-Ghābah.’ ‘Umar ibn al-Khattāb heard this and said: ‘No, by Allah! Do not leave him until you receive what he owes you.’ He then said: ‘The Messenger of Allah (peace and blessings be upon him) said: “Gold for silver is usury unless exchanged on the spot; wheat for wheat is usury unless exchanged on the spot; dates for dates are usury unless exchanged on the spot; and barley for barley is usury unless exchanged on the spot.”’”
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Thus, in currency exchange or in the sale of gold for gold or silver for silver, neither a mutual promise to transact nor