Shari'a (the Law of Islam) recognizes no difference between the religious and secular life. It governs every aspect of the believer's journey through life and of the nations ruled by it. Shari'a means "the path to the watering place". It covers criminal law, oaths, contract law, evidence, judicial procedure, marriage, family inheritance, slavery, education, personal hygiene, the killing of animals, manners and deportment and it is interpreted when necessary by religious scholars who sit as judges.
The Law finds four sources in the Islamic world: The Qur-an (the word of God), the Hadith (traditions of the prophet) and when these sources are silent, consensus or Ijma' a of those learned in the law, and Qiyas - analogy or deduction from a study of the Qur-an of the proper way to decide. The Shi'a would disagree with Ijma' as a source of Law and prefer to rely on the infallibility of their Imam. Never the less, the concept of JUSTICE under God's law is critical to understanding Islam.