Is it permissible for a sick man on the verge of death to sell half of his wealth even though he has heirs?

If a man is conscious and aware of what he is doing, then his sale of his property is permissible, unless it involves preferential treatment for others. This is the view of the Malikis, Shafi'is, and Hanbalis. However, if he is unconscious due to a change in his mind because of old age, then he is interdicted and prevented from disposing of his property.