There are many unlawful transactions; some of them are as follows: 1. * buying and selling intoxicating drinks, non-hunting dogs, pigs, and – based on obligatory precaution (al‑iḥtiyāṭ al‑wājib) – impure (najis) carcasses, except for what is removed from a living human body to be transplanted into another body.
Apart from these, buying and selling an intrinsic impurity (ʿayn al‑najāsah) is permitted if it is for some significant and lawful use, such as buying and selling impure animal waste for use as fertilisers; 2. buying and selling usurped (ghaṣbī) property, if this necessitates having disposal over it, such as handing it over and taking possession of it; 3. * transactions with money that is no longer legal tender or with counterfeit money, if the other party is unaware of this.
If he is aware, the transaction is permitted if that money has a significant value; 4. transactions of unlawful objects; that is, things that have been made in a form that is usually utilised in an unlawful manner and its value is due to its unlawful utilisation, such as idols, crucifixes, gambling implements, and instruments of unlawful entertainment; 5. transactions in which there is deceit.
It is reported that the Most Noble Messenger (Ṣ) said, ‘One who deceives Muslims in his transactions is not one of us. Allah takes away the blessing of his sustenance, closes the path of his livelihood, and leaves him to himself.’ Deceit can take place in different ways, such as: a. mixing a good item with a bad one or with something else; for example, mixing milk with water; b.
making an item appear better than it really is; for example, spraying water onto old vegetables to make them appear fresh; c. feigning an item as something else; for example, gold-plating an item without informing the buyer [that it is not solid gold]; d. concealing a defect in an item when a buyer trusts the seller not to conceal defects.