In Islam, the system a specific religious institution revenues from property. Such institutions are usually mosques, religious schools or social institutions, like hospitals.
A waqfs would normally be arable land, farms, oases, buildings or companies. To the waqf there are managers in charge of securing that all maintenance and profits are well taken care of.
In the early centuries of Islamic history, during times of territorial advances, waqfs were vital to the establishment of social structures in lands with weak state structures.
In modern times, waqfs are merely financing structures, but can in many cases be of great importance. The waqf is thought of as a part of the whole mosque structure.
A very central element to a waqf is its permanence. Once a waqf has been established, there are no possibilities for alterations of the contract. The only exceptions for this, is when some of the involved violates the contract or if the founder or manager secedes from Islam. Also, plain money is in most cases not seen upon as waqf.
The Muslim part of the origin of the waqfs, is a bit obscure, and waqfs are seldom mentioned in the Sunna. There appears to have be a mixture of pre-Islamic and non-Islamic traditions. There have always been regional differences in the ways of regulating the waqfs. The institution of waqfs is only briefly described in the Sharia, Muslim law.
To secure inheritance
While the benefits from a waqf can be pious and good, the initial intent to create one can in some cases be more complex. In many Muslim societies thoughout history, regulations on inheritance have represented a problem for rich families: legal systems have in many cases lacked systems to allow property to pass on to the descendants. Inheritance in such cases have simply been transferred to the ruler of the province or country.
Waqfs had, on the other hand, regulations to make children guaranteed trustees, having the right to claim about 10% of the total revenues. This has been of great importance promoting the popularity of waqfs.