What is the Islamic ruling on the issue of Waqf?

Endowment (Waqf) is the inalienability of the principal and the dedication of its usufruct (manfa'a) for charitable purposes. It is a recommended act of worship (qurbah) in Islam, as evidenced by authentic Sunnah and the consensus of the Imams. It is established by a declaration or an act that indicates it. It is a condition that the endower (waqif) be legally competent to dispose of property, and that the endowed property (mawquf) be something from which continuous benefit can be derived, be specifically identified, and dedicated for a righteous cause. A temporary or conditional endowment is not valid, except if conditioned upon the death of the endower. The conditions stipulated by the endower must be observed, unless they contradict Islamic law. If no supervisor (nazir) is appointed, or if the appointed supervisor dies, the supervision falls to the beneficiary (mawquf 'alayh) if specifically identified, otherwise to the ruler. Endowment is a binding contract and cannot be revoked, unless its benefits become entirely defunct, in which case it may be sold and its price spent on a similar endowment.