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The economic value of a commodity is determined by two factors:
1. The commodity offers a particular benefit, making it coveted by rational people, such as things which are edible, consumable or wearable.
2. A body that is vested with the authority, sets a value for the property, such as currencies and stamps which are valued by the government.

2866. Buying and selling is different from loaning, both in terms of the subject and also the precepts. In terms of the subject, buying and selling is the act of exchanging a corporeal property for another in its attribution, be it an attribution of ownership or proprietorship. Loaning is the act of giving ownership of a corporeal entity to the party that is acquiring the loan, in return for a substitute if the item is fungible, and for its value if it is not fungible.
In terms of their precepts, the following are some areas where they differ:
1. Interest in sales differs from interest in loans. In a loan, any additional amount that is stipulated is interest and forbidden. However, in a sale, it is only forbidden if the item that is sold and the item acquired in return are both of the same type, and they are sold by weight or volume. In this case, any extra amount is interest and it is forbidden. Hence, if they are not of the same type, or they are not sold by weight or volume, it is not forbidden to take an extra amount, such as the case in commodities which are sold by count.
2. If a sale involves interest, it will invalidate the sale, and an exchange of ownership will not be realized. However, in the case of a loan, stipulating interest will not invalidate the loan. The debtor will become the owner of the loaned item. However, the creditor will not become the owner of the stipulated excess.

2867. All paper money, such as Iraqi dinars, American dollars or Iranian tumans, have economic value, because their respective governments have set a value for their paper money, which is accepted and common in all countries. It is for this reason that it has economic value, and they may cancel its economic value and validity at any time.
It is obvious that such money is not sold by weight or volume, and hence some of the jurisprudents (may the Lord raise their status) have said, “It is permissible to exchange this money for more or less of the same kind. It is also permissible to give this money in cash for a debt being owed, for less than it or more than it.”
However, to exchange something that has an arbitrary economic value, and is purchased and sold by count, for something more or less of the same kind is problematic.
In the event that the owner of the greater amount reaches a compromise settlement with the owner of the lesser amount, in that the owner of the greater amount would gift it to him, and he too would gift the lesser amount to him, then it will not be problematic. For example, the owner of nine hundred dollars would state to the owner of a thousand dollars, “I compromise with you that you would gift a thousand dollars to me and in return I would gift nine hundred dollars to you.”

2868. Bills of exchange which are common amongst businessmen and people, and are used to carry out transactions, are not like currency notes which have an arbitrary economic value; rather, they are certificates of a loan that is liable on the payer and the signatory of the bill. Hence, when a buyer gives a bill of exchange to the seller, he has in fact not paid the price of the purchased commodity. Therefore, if the bill of exchange gets lost or burnt whilst it is in the possession of the seller, nothing will be lost of his property, and neither will the responsibility of the buyer be lifted. However, if he pays for the price of the commodity with paper money, and then the money gets lost, it will be deducted from the property of the seller and he will incur the loss.

2869. Bills of exchange are of two kinds:
1. A bill of exchange which is reflective of a real loan, meaning that the signatory in reality owes the amount mentioned in the bill to the payee, and the bill is a record of that loan.
2. A bill that is not reflective of a real loan; rather, it is only imaginary.
In the first kind, wherein the payee is in fact owed a time-specific loan, selling the bill for an amount that is more or less is not problematic, given that there is a difference (in the two), such as dollars for pounds, and given that it is not the price of a credit based transaction. However, if there is no difference, such as selling dollars for dollars, then it is problematic. However, if the transaction is carried out in the form of a compromise settlement as elaborated in article 2867, it will not be problematic.
In the second type, where the bill is imaginary, the payee cannot sell it to another person, since he is not owed anything by the signatory of the bill; rather, the bill of exchange was issued so that the payee would be able to make use of it. The manner of using it according to the shari’a is in the following manner: The payer deputizes the payee to sell the amount mentioned in the bill—such as 50 Saudi riyals which are worth 11,000 Iranian tumans—on his behalf to the bank for another kind of currency for a lesser value, such as 10,000 tumans, and also deputizes him to then sell the 10,000 tumans on the behalf of the payer to himself for the price of 50 Saudi riyals.
In this manner, the payee becomes indebted to the payer in the amount that the payer has become indebted to the bank, which is 50 riyals.
Another manner would be a case where the bank loans the amount of the bill to the payee, and in return the payee pays an amount to the bank as documentation fees, without it being stipulated by the bank. However, if it is stipulated as a condition, even if it be non-explicitly understood, it will be considered an interest-based loan.
There is no problem for the payer to demand the amount of the bill from the payee, and acquire it from him, because the payee has transferred his debt to the bank in its entire amount from the bank to the payer.