Is it permissible for the heirs to sell, demolish, and distribute the endowment (waqf) left by their grandfather, which he explicitly designated as inalienable and prohibited his heirs from disposing of, and whose features have deteriorated? And is invoking the grandfather after his death legitimate?

If the grandfather executed the endowment (waqf) during his lifetime and in good health, it is a valid endowment that must be acted upon. However, if he postponed it until his death, it is a bequest (wasiya) from which no more than one-third can be executed except with the consent of the heirs. It is not permissible to dissolve the endowment or dispose of it in a way that removes it from its endowment status. It is permissible to sell and replace it if its benefits have completely ceased, or to sell part of it to maintain the rest, or if its benefit is very minimal. The grandfather's imprecation against anyone who violates his bequest is rightful if the endowment is valid and enforceable.