What makes masturbation forbidden despite semen being discharged in marriage, adultery, and masturbation? What is the difference between them? And what makes it harmful to health only in the case of masturbation?

The difference between semen discharge due to masturbation and fornication, and its discharge due to marital intercourse, is like the difference between money earned through lawful means and that earned through unlawful means. The semen is one and the same, but the method differs. In the former case, a person is rewarded if they intend it as an act of drawing closer to God, while in the latter, they are burdened with sin in all circumstances.

Therefore, Islamic law has forbidden masturbation and fornication and blocked the ways leading to them. It prohibits lowering the gaze and avoiding mixing. As for those who cannot marry, they should fast. Regarding the reasons for the harm in masturbation, as opposed to other acts, the answer lies with medical professionals. The general principle is that "whatever is proven to be harmful is forbidden to consume." Harm is negated when semen is discharged through marital intercourse, because it is a lawful path, and Almighty Allah does not legislate for His servants that which would cause them harm.