A contemplation about the reasons for illegality of Gazaf sale

The famous Imami Jurisprudents believe that a conjectural transaction makes a sale contract null and void while nowadays in a lots of cases , there is no possibility of accurate information about the subject-matter of the contracts. In a descriptive- analytical method and library way, this paper has considered and analyzed the amount of validity of such a claim. The results of this research show that the traditionswhich are referred by the Jurisprudents to nullity of Gazaf sale do not indicate their claim and they are more special than the mentioned claim. Moreover, it seems that in the supposition of question, the instruments of weighing a goods are not important, but the criterion is to be specified the subject matter of a contract in a way that does not cause any difference, and this significant issue can be determined by observation and customary confidence methods.