What is the ruling on masturbation and its consequences, and does the emission of a very small amount of semen necessitate ghusl (ritual purification)?

The practice of masturbation is forbidden, and its expiation is sincere repentance to Allah the Almighty, for "the one who repents from sin is like one who has no sin." If semen is discharged due to this habit or another pleasure, then that necessitates ghusl from janabah.