Legal opinions in Islamic Law (or Shariah) are derived from the primary sources of Islam: the Qur’an and hadiths, which contain guidance on how Muslims should behave. In Sunni Islam, four other sources of legal opinion beside these two primary sources are recognized: consensus (ijma), analogical deduction (qiyas), juristic discretion (istihsan), and principles of public welfare or interest (maslaha). Shia Muslims recognize the same additional four sources but also add three more: individual reasoning (aql), custom or precedent as accepted by a given community over time (‘urf or ‘ada) and witness/testimony (‘adl).

The Qur’an is seen as the word of God revealed to Prophet Muhammad through archangel Gabriel over 23 years. It is written in an Arabic script that has remained unchanged since its revelation about 1,400 years ago. Every Muslim believes it to be the unaltered “final” message from God and therefore is considered an authoritative source for understanding Islamic beliefs and practices. The Sunnis believe that any interpretation must come from within its verses while Shias believe that some interpretations require combining multiple verses together along with other methods such as analogy to determine their meaning.