Recurrent are the conditions set by a seller or a buyer when concluding a trade transaction. Accordingly, it has become a necessity to study and tackle the different kinds of such conditions, pointing out the legal and the illegal ones among them. The scholars of Islamic Jurisprudence, defined a condition (of a trade transaction) as follows: "It is obligating one of the two parties (of the sale) by the other for the benefit of the latter." According to them, a transactional condition is invalid unless it is made at the time of the transaction and embedded in the transactional contract. In other words, a condition is invalid if made before or after concluding the contract.

　　In general, the conditions in trade transactions are divided into valid conditions and invalid ones.

　　First: Valid Conditions

　　Valid conditions are those that do not contradict the objective of the contract. Such a kind of condition obligates its fulfillment; the Prophet said: "Muslims must keep to the conditions they make." [Abu Daawood & At-Tirmithi]

　　Such conditions obligate fulfillment also because all conditions in trade transactions are originally legal except for those invalidated and prohibited by the Lawgiver (Allah Almighty). The valid conditions are of two kinds:

　　1- The first kind is the invalid illegal condition that basically nullifies the selling contract, such as when one of the two parties stipulates another contract within the main one. For example, it is an illegal condition when a seller of a commodity makes a condition that the buyer must make him his partner in business, lend him a sum of money, or allow him to share his house, etc., or that he says, "I sell you this commodity on the condition that you rent me your home." Such a condition is legally invalid so it nullifies the original contract. This is because the Prophet forbade concluding a selling contract based on another conditional contract. (At-Tirmithi & An-Nasaa'i) This Prophetic prohibition was interpreted by Imaam Ahmad Ibn Hanbal exactly as we have pointed out above.

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