The Fundamentals of Expediency Convention in Legal Status Deduction

The present article aims at investigating the fundamentals of expediency convention as a strategy in legal status deduction.
The method of the survey is qualitative research and comparative- analysis approach in studying the theological and jurisprudence texts.
The results of the present research indicate that the convention of expediency is discussed in two fields: before the absolutely clear Text and after it. In the field of before the clear Text (the commands of religion in accordance withbenefits and depravities) wisdom and rationality is considered as an important place in general benefits; although there are different ideas on the area which rationality is able to recognize the benefits and depravities. In the field of after the clear Text (goals of religion) which has more supporters among the Sunnis scholars, any expediency in accordance with great goals of religion is considers as authority (proof) although there are many differences in the ideas of people of the Sunnah on the great goals of religion.
The author of the research concludes the canonic rules are generally based on expediency; but there is no need to be devoted to only rules. It may be originated in divine legislation meaning that the mere legislation of the rule is a sort of expediency. On the other hand if we find expediency in accordance with the supreme goals of the religion, we consider it as our proof (authority).