Is it permissible for a wealthy father to take a portion of his deceased wife's money designated for ongoing charity, after the heirs have agreed to that?

If the heirs pronounce the word waqf (endowment) explicitly or by implication, or perform an action indicating waqf with the intention thereof, then it is not permissible for any of them to retract it, according to the preponderant opinion, because the property thereby exits their ownership. Jurists have differed regarding the binding nature of waqf. The majority of jurists (Malikis, Shafi'is, Hanbalis, and Abu Yusuf and Muhammad from the Hanafis) hold that once a waqf is issued by someone competent to dispose of property and fulfills its conditions, it becomes binding, and the endower's right to dispose of the endowed property is severed. This is based on the Prophet Muhammad's (peace be upon him) saying to Umar ibn al-Khattab (may Allah be pleased with him): "Endow its essence, and it is not to be sold, gifted, or inherited." Abu Hanifa, however, held that waqf is permissible but not binding, and the endower may retract it, though it is disliked. However, it becomes binding by a judge's ruling or if it takes the form of a will. Nevertheless, the fatwa among the Hanafis is based on the opinion of Abu Yusuf and Muhammad, which states its binding nature.

However, if what occurred from the heirs was merely a promise of waqf or an intention without a form or action indicating it, then it is permissible for whoever wishes among them to retract it, although fulfilling this promise is more virtuous.