Is a husband rewarded or sinful if he gives a perpetual charity (ṣadaqah jāriyah) or establishes an endowment (waqf) for his deceased mother and her husband from her salary, without her knowledge, knowing that she does not comprehend the meaning of an endowment?

It is not permissible for your husband to give charity from the money of his mother, who suffers from dementia and loss of consciousness, as she is considered like an insane person, and her guardian is not allowed to dispose of her money. If she were fully conscious and of sound mind, it would not be permissible to give charity from her money except with her permission. If she refused, it would not be permissible to give charity from her money without her knowledge, because it is disposing of another's money without permission. As for her deceased husband, he does not have money from which charity can be given on his behalf, for upon his death, ownership of his property transfers to his heirs. Giving charity on his behalf from the money of the deceased old woman is misplaced.