2090. Buying or selling oil which is derived from an animal after its death is not valid, and consuming the oil is not permissible.
It is also not valid to buy or sell leather products which are acquired from a Muslim, whom a person knows to have acquired it from a k¡fir, and also knows that he has not bothered to investigate whether the leather was acquired from an animal slaughtered according to Islamic law, or not. It will not be permissible to offer prayers with such a product.

2091. A transaction that involves intoxicating drinks is both invalid and forbidden.

2092. The sale of a usurped property without the consent of the owner is void. The seller must also return to the buyer the money that he acquired from him.

2093. If a buyer intends to engage in a transaction, but also intends not to pay the price of the commodity that he is buying, the transaction will be valid and it is obligatory for him to pay its price to the seller.

2094. If a buyer purchases an item with an abstractly defined payment, and pays for it with wealth that was acquired illegally, the transaction will nonetheless be valid. However, as long as he does not pay off the liability with wealth that is acquired legally, he will not be absolved of his responsibility (to pay the seller).

2095. The purchase and sale of instruments of entertainment, such as guitars and lutes is forbidden. This ruling, when applied to small guitars which are used as toys by children, is based on precaution. As for instruments which are dual-purpose, such as mp3 players and voice recorders, there is no harm in buying or selling such items as long as they are not meant to be used in a forbidden manner.

2096. If a thing which can be used in a legal manner, is sold to a person who uses it in an illegal manner for the express purpose that he use it in an illegal manner, then the transaction will be both invalid and forbidden. An example of this is selling grapes with the understanding that they will be made into wine. However, if he does not sell it with this intention, but is only aware that the buyer will make wine with it, there will be no problem in it.

2097. It is forbidden to make sculptures of living things, and so is—based on obligatory precaution—illustrating images of it. However, buying, selling and keeping it, is permissible, though better to avoid.

2098. Transactions carried out with items acquired through gambling, stealing, or void transactions, are uncommissioned. Their validity and sanctioning is contingent on the permission of the owner or his guardian. Any use of the item is forbidden, and the person who possesses it must return it to the owner or his guardian.

2099. If a person sells ghee that is mixed with suet, and the transaction is based on particularized goods, such as the case wherein the person states, “I am selling these three kilograms of ghee,” then such a transaction can take two forms:
1. The amount of suet mixed in the ghee is to an extent that it would still be deemed three kilograms of ghee in the common understanding, albeit an adulterated form of it. In this case the transaction will be valid, but the buyer will maintain the right to cancel it.
2. The amount of suet mixed in the ghee is to an extent that it is no longer deemed to be three kilograms of ghee in the common understanding; rather, they view it as a mixture of ghee and suet. In this case, the transaction is invalid in proportion to the amount of fat in it. The money that the seller acquires for the suet in the mixture belongs to the buyer, and the suet belongs to the seller. In fact the buyer may also cancel the transaction with respect to the pure ghee within the mixture.
If however the transaction is not based on particularized goods, rather the sale is based on three kilograms of ghee in an abstractly defined form, and later the seller delivers ghee mixed with suet, the buyer reserves the right to return the adulterated ghee and demand pure ghee.

2100. If an amount of a commodity that is sold based on weight or volume, is sold for a greater weight or volume of the same commodity, such as one kilogram of wheat sold for one and a half kilograms of the same, it is interest and therefore forbidden. The transaction is also void. The same will apply if one of them is faultless and the other is defective, or one of superior quality and the other inferior, or if they are subject to a difference in price. Should the sale and purchase be based on the difference in their amounts, it will still be interest and forbidden. The transaction will also be void.
Therefore, if a person gives unbroken copper and acquires in return a greater amount of broken copper, or gives rice of superior quality and acquires in return a greater amount of inferior quality rice, or gives finished gold and acquires in return a greater amount of raw gold, it is interest and forbidden. The transaction is also void.

2101. If the additional asset acquired from the transaction is other than the commodity being sold, such as a the sale of one kg of wheat for one kg of wheat and two dollars, it will still be interest, and therefore forbidden. The transaction will also be void.
In fact, even if the seller does not take any extra goods, but stipulates that the buyer should render some services to him, it will again be interest and therefore forbidden. The transaction will also be void.

2102. If one wishes to avoid interest based transactions in the sale and purchase of commodities that are measured by weight or volume, he must be careful to ensure that an excess or that which is subject to the rulings of an excess—as elaborated in the previous article—does not occur on either sides of the transaction. For example, one may sell one kg of wheat and one handkerchief for one and a half kg of wheat in immediate payment, so that the extra half of a kg of wheat would be in lieu of the handkerchief. The same applies in a case where there is an excess on both sides, such as the sale of one kg of wheat and one handkerchief for 1.5 kg wheat and one handkerchief, by considering what was elaborated earlier.

2103. If a person sells a commodity that is sold in meters or yards, such as cloth, or a commodity that is sold per piece, such as eggs or walnuts, and takes more in return, there is no problem in it as long as the transaction is based on two particularized commodities.
The same will apply if it is sold in an abstractly defined manner, and there is a distinction between the two, such as the sale—in an abstractly defined manner—of 10 large eggs for 11 medium eggs. However, if there is no distinction between the two, to claim the validity of the transaction is problematic.
The same will also apply to the sale of currency notes—even though it is a countable item—in return for more, in the event that they are of the same currency, regardless of whether they are both particularized or abstractly defined. To claim the validity of such a transaction is also problematic.

2104. The goods that are sold by weight or volume in some cities, and by count in other cities, will—in each city—be subject to the ruling of the method that is conventional in that city, given the absence of an overriding tendency between the two methods. The same will apply if it is sold by weight or volume in most cities, and by count in some cities. In the latter case, the precaution is that the commodity should not be sold for something more than its value.

2105. If the commodity being sold is not the same as the item being received in lieu of it, there is no problem in taking more. Hence, if someone sells one kg of rice, and takes two kgs of wheat in return, the transaction will be valid.

2106. If the commodity being sold, and the one being received in return are both derived from the same origin, one should not take any excess in the transaction. Therefore, if a person sells one kg of cow’s ghee and takes one and a half kg of cow’s cheese in return, it will be interest, and hence forbidden. The transaction will also be void. The same applies if ripe fruits are bartered for unripe fruits of the same kind.

2107. In the rulings pertaining to interest based transactions, barley and wheat are considered to be of one species. Therefore, if—for example—a person gives one kg of wheat and takes in return one and a half kgs of barley, the transaction will be interest based, forbidden and void. Similarly, if a person takes 10 kgs of barley, in return for giving 10 kgs of wheat at the beginning of the harvest, then because he is acquiring the barley immediately and delivering the wheat after a while, it is as if he is acquiring something extra, and therefore the transaction is forbidden and void.

2108. A Muslim may take interest from a non-Muslim who is not under the protection of Islam. As for a non-Muslim who is under the protection of Islam, it is not permissible to carry out an interest based transaction with him. However, if the transaction has already been carried out, if taking interest is permissible in the non-Muslim’s religion, he may take it.
Additionally, a father and son, or a husband and his permanent wife may take interest from each other.

The Conditions of the Buyer and the Seller
2109. The following conditions have been stipulated for the buyer and the seller:
1. They should both be b¡ligh
2. They should both be sane
3. They should not be feeble-minded, in the sense that they should not be wasting their property on pointless ventures.
4. They should have the intention to buy and sell. Hence, if someone jokingly states, “I sold my property,” a transaction will not be realized. In reality, the intention is not a condition for the validity of the transaction; rather, it is what forms the transaction.
5. No one should have wrongfully compelled them. If they are compelled, but later consent to it, the transaction will be sanctioned.
6. They should be the owners of the commodity and the thing being offered in return, or have the right of guardianship over the owners, or deputyship and permission from him.
The detailed rulings pertaining to these conditions will be elaborated in subsequent articles.