What is the ruling of Islamic law on selling the heirs' share of an endowment (waqf dhurri) that is documented only with the village sheikh, especially given the heirs' need for money?

The endowment (waqf) by a father of his property for his children is valid if it is immediate and out of his possession; otherwise, it is void due to lack of ḥawz (taking possession). It is also void if it is a bequest to an heir. Scholars have differed on what can be endowed, and the majority opinion is that only that from which benefit can be derived while its substance remains intact can be endowed. Accordingly, what your father endowed of houses, animals, real estate, machinery, and furnishings is valid, while what he endowed of food, drinks, cash, and the like is not valid. Therefore, what was validly endowed may not be sold, and what was not validly endowed may be utilized in any way.