The Qur'an
The Qur'an is where all the messages Muhammad received from God are stored. The Qur'an teaches Muslims that there is only one god-Allah-and that Muhammad is his prophet. The Qur'an says people must obey Allah's commands. The Qur'an describes acts of worship, guidelines for moral behavior, and rules for social life. The Qur'an also has to do with jihad, which means "to make an effort or to struggle."
The Sunnah
The Sunnah is based on the hadith, the written record of Muhammad's words and actions. The Sunnah refers to the way Muhammad lived, which provides a model for the duties and the way of life expected of Muslims. This means the Sunnah guides Muslim behavior. The Sunnah provides guidelines for relations in business and government and the Sunnah has other examples which form the basis for rules on how to treat others.
Islamic Law
The Qur'an and Sunnah also form the basis of Islamic law, or Shariah. Shariah is a system based on Islamic sources and human reasons that judges the rightness of actions an individual or community might take. The Shariah sets rewards for good behavior and punishments for crimes.