Abstract
In every legal system in the world, some elementary principles are formulated by the experts or legislature which work as the sources of law and recognized by jurists. Some legal rules, however, are not laid down by the legislature or experts but grow instead from informal social practices. These are known as customs and usages in legal terms. Custom is a matter on which a community of people agrees in the course of their daily life, and common usage is an action which is repeatedly performed by individuals and communities. When a community makes a habit of doing something, it becomes its common usage. The custom or common usage of a community shares the same underlying idea even if what is understood by them differs slightly. In contract law, for example, the customs of merchants are used by the courts to interpret the provisions of business contracts; in tort law, customs of best practice are used by courts to define professional responsibility. This article studies custom and usage as a source of Islamic Fiqh and its application in Shariah Law.