We know istimna is haraam in Islam. But there is a certain medical condition for which sometimes doctors prescribe the patients to do that regularly.
Now I was wondering, say a person had a wife who died and he cannot marry again because he still loves his previous wife. But he suffers this kind of disease and is prescribed to do either intercourse or istimna regularly. Now a halaal solution here would be to marry again for this purpose. But is that really a solution, considering marrying again would destroy him mentally and his love, and he knows very well he cannot love his second wife?
Does he have to marry just for a physical treatment? Or in that situation, can he do istimna, just for the sake of the treatment, and not for enjoyment or anything?