What is the ruling on a 70-year-old retired man, who has lost both his wives, practicing masturbation four or five times a month, on the grounds that his doctor advised him to do so to avoid blockage of the prostatic duct due to benign prostatic hyperplasia?

Whoever is able to marry should hasten to do so, for it is from the guidance of the Prophets. The Prophet, peace and blessings be upon him, encouraged youth to marry if they are capable, as it is more lowering of the gaze and more protective of one's chastity. And whoever is not able, let him fast. If a person fears falling into forbidden acts, marriage becomes obligatory for him, even if he does not possess sufficient wealth to fulfill the wife's rights, provided he informs the woman of this. As for one who is unable to marry due to poverty, he must practice self-restraint (abstinence). Masturbation is forbidden, and mere apprehension of harm does not permit it.