مسائل المنتخبه (Articles Of Islamic Acts) - الخوئي، السيد أبوالقاسم - الصفحة ٤٢٩ - UNLAWFUL TRANSACTIONS

utilized for an unlawful act only (e.g. gambling tools).
(vi) To sell a thing in which something else is mixed and it is neither possible to detect the adulteration nor the seller informs the buyer about it (e.g. to sell ghee mixed with fat). This act is called cheating (ghash) or adulteration. The holy Prophet of Islam has said: "If a person sells something to the Muslims or harms them, or practices deceit upon them, he is not one of my followers. And as and when a person cheats his brother Muslim (i.e. sells him an adulterated commodity) Allah deprives him of his livelihood, closes the means of his earnings and leaves him to himself (i.e. deprives him of His blessings).
٢٠٦٤. There is no harm in selling a pure thing which has become impure and can be purified by washing it with water. However. if the buyer wants to utilize it for apurpose for which purity is a condition precedent, for example if it is a kind of food which he wants to eat the seller should tell him about its being impure. In case,however. it is a dress it is not necessary that the buyer should be told about its being impure though he may use it for offering prayers. because in prayers the apparentpurity of body and dress is sufficient.
٢٠٦٥. If a thing like ghee and oil, which cannot be purified by washing with water, becomes impure and if it is to be used for a purpose for which purity is a condition precedent (e.g. if ghee is required for eating) it is necessary for the seller to inform the buyer about its being impure. And if it is required fora purpose for which its purity is not a pre-requisite. for example if impure oil is to be used for burning. but it is possible that the food or body of the buyer may become impure with it. even then the same rule applies and it is necessary for the seller to inform the buyer about the impurity of the commodity because it is not permissible to become the cause of the impurity of food or of the impurity of body which becomes the cause of nullification of ablutions or bath becoming void.