Is it permissible for the heirs to dispose of a house that the deceased designated as a charitable endowment (waqf) before his death, and to consider it an inheritance?

If the deceased woman endowed her house while in good health, then the heirs have no right to it, because it has become an endowment (waqf) that cannot be sold, gifted, or inherited, just as Umar ibn al-Khattab (may Allah be pleased with him) did with the land of Khaybar. However, if she endowed it during her death illness, then it takes the ruling of a will (wasiyyah (definition)) which is only enforceable up to one-third of the estate. Any amount exceeding one-third is dependent on the heirs' approval. If the house does not exceed one-third of her wealth, then all of it is an endowment. If it exceeds one-third, the will is executed for an amount equivalent to one-third, and the remainder depends on the heirs' consent; otherwise, they divide it as inheritance, due to the attachment of the heirs' right to the wealth during the death illness.