The Prophet, sallallaahu alayhe wasallam, prohibited some forms of sales that people were known to use during his time. The wisdom behind this prohibition of some sales is to facilitate ease for people and not to increase prices for them. Also, it is designed to stop sales that might include risk or trickery and eliminate any sale that might instigate hatred and enmity amongst people.

1. The Prophet, sallallaahu alayhe wasallam, prohibited that a town dweller (urban resident) be allowed to sell the goods of a desert-dweller (rural resident), as stated in an agreed upon hadeeth. This means that the urban resident is prohibited from selling the goods of a rural resident on behalf of the latter. This is because the urban resident might wait until people are in need of the goods and then raise the prices. Anas Bin Malik said, "We were forbidden to allow a town-dweller to sell the goods of a desert-dweller, even if the latter is a brother from the same mother and father.” (Agreed upon)

2. The Prophet, sallallaahu alayhe wasallam, prohibited najash. Najash is trickery whereby one offers a high price for a commodity not intent upon buying it but upon cheating someone else who wants to buy it, even though it is not worth such an elevated price. Scholars have unanimously agreed on the prohibition of such action if the increase in price puts the commodity at a higher price than similar items. This prohibition is based on the hadeeth narrated by Ibn Umar that Allah's Messenger prohibited najsh. (Agreed upon)

   Even if the price is increased to the price of a similar commodity, al-jumhoor (the majority of scholars) have gone with the impermissibility of such actions based on the generality of the hadeeth text. Ibn Hazm, Ibn Abdul-Barr and Ibn al-Arabi, however, held the opinion permitting such action. Ibn al-Arabi stated that, "If a man sees a commodity that is sold below its actual value and he increases the value to the correct value, then he should not be accused of najash, especially if he did not have bad intentions." This is supported by the hadeeth narrated by Imaaam Ahmad that the Prophet, sallallaahu alayhe wasallam, said, "Leave the people alone, for Allah sustains some from others. Should one ask his brother for a sincere advice, his brother should give him advice."

    

3. The Prophet, sallallaahu alayhe wa sallam, prohibited meeting caravans on route with the intention of purchasing goods before the sellers know the market price. Ibn Mas'oud narrated that the Prophet, sallallaahu alayhe wasallam, prohibited going to meet the vendor on route in an agreed upon hadeeth. Ibnul Qayyim said, "The Prophet, sallallaahu alayhe wa sallam, prohibited that because it includes deception of the seller who does not know the market price."

4. The Prophet, sallallaahu alayhe wasallam, prohibited the Muslims from persuading buyers to cancel their purchases from other vendors, and then sell them his goods. This is tantamount to saying to someone who is buying an item for ten dollars, "I have the same item for seven dollars for you." The Prophet, sallallaahu alayhe wasallam, also prohibited a Muslim from entering into a transaction to purchase a commodity when his brother Muslim has already negotiated a purchase of that same commodity. For example, one says to a vendor selling a commodity to one person for seven dollars, "I will buy it from you for ten dollars." Ibn Umar narrated that Allah's Messenger, sallallaahu alayhe wasallam, said, "Do not urge someone to return what he has already bought from another vendor so as to sell him your own goods. And don't urge a woman who is engaged to someone else to cancel her engagement so that she can become engaged to you, except with the permission of the other person." (Ahmad)

5. It is also prohibited to sell a commodity that might be used in the commission of sin. This would include selling juice to someone who uses it to make khamr (intoxicants), selling weapons during periods of fitnah (confusion or instability), or selling a house to someone who will use it for sinful deeds. Allah says, "And do not help one another in sin and transgression." [5:2] This prohibition is based upon knowledge of the intention or evidence supporting the suspicion.

6. It is also prohibited to sell one debt for another debt. Imam Ahmad had stated that there is no sound hadeeth on this issue but people have unanimously agreed that it is not permissible to sell one debt for another debt.

7. There is also a prohibition of injustice in sales, especially when the buyer does not know the price, or he is not good in bargaining. A person came to the Prophet, sallallaahu alayhe wasallam, and told him that he was always betrayed in making purchases. The Prophet, sallallaahu alayhe wasallam, then told him, "Say at the time of buying: ‘no cheating'." (Agreed upon) Cheating and deception are both prohibited. The Prophet, sallallaahu alayhe wasallam, said "Both cheating and deceiving are in the fire (meaning lead the person to the Fire)." (Ibn Adiyy)

8. It is prohibited to sell goods before taking them into possession. The Prophet, sallallaahu alayhe wasallam, said to Hakim ibn Hizam, "Do not sell what you have purchased until you receive it." (Ahmad) Ibn Abbas narrated that Allah's Messenger, sallallaahu alayhe wasallam, said, "He who buys foodstuff should not sell it until he takes all the measure which he has bought in full." (Agreed upon) Ibn Abbas stated that all types of selling should be done similarly.

   Ibn Umar said he saw people at the time of the Prophet, sallallaahu alayhe wasallam, buying foodstuff but would not sell it until they brought it to their places (Agreed upon) The followers of math-hab Ahmad ibn Hanbal went with the opinion that only foodstuffs that are measured or weighed should be dealt with in this manner. Other foodstuffs can be sold before taking them into possession.