Is it permissible to take money from the father without his knowledge to spend on sisters if the father is unable to manage his financial affairs, and must the amount be returned?

Your action of taking money from your father without his permission is incorrect, because it is an unlawful encroachment upon his property, and you must return it to him or to his guardian. If the father has lost his mental capacity, his children are not permitted to dispose of his money except with the permission of the legal guardian, appointed by the father or by a judge. It is not permissible for children to take anything from their father's money without his permission, unless he withholds the obligatory maintenance due to them.