All banks in Iran must follow the banking principles and practices described in the Islamic banking law of Iran passed in 1983 by the Islamic Majlis of Iran. According to this law, banks can only engage in interest-free Islamic transactions (interest is considered as usury or riba and is forbidden by Islam and the holy book of Quran). These are commercial transactions that involve exchange of goods and services in return for a share of the assumed "profit". All such transactions are performed through Islamic contracts, such as "Mozarebe", "Foroush Aghsati", "Joale", "Salaf", and "Gharzol-hassane". Details of these contracts and related practices are outlined in the Iranian Interest-Free banking law and its guidelines.