The Difference between Customary Authority in Islamic Jurisprudence and Schools of Thought

First of all, it should be said that custom is not a new phenomenon, but it is the same method and continuous behavior among people, which Islamic jurisprudence and law have approved in some cases and rejected in others. Despite this, it is considered as one of the main and practical documents for discovering concepts and meanings. By examining the background of custom, it is clear that many materials have been written about custom in various directions, but it is a matter that has been obscured and jurists and jurists have not paid much attention to it. The validity and non-authenticity of the custom is that there are differences of opinion between Shia scholars and different schools of thought and they have not reached a solid theory about it. In this article, the main goal is to investigate the differences of opinion on the validity of custom in Shia jurisprudence and Islamic schools of thought and to find a reliable and valid reason to prove how Shia jurisprudence considers custom only as a tool to reach the conclusion of Sharia and legal rulings. And the jurists of different schools of thought, including Hanafi, consider the common law to be the authority in all other rulings, except for obligatory rulings, such as: Istihsan.