What is the ruling on the emission of semen (maniyy) or prostatic fluid (madhiy) after a head massage at the barbershop, and does it necessitate ghusl (ritual bathing)?

The emission of semen or the like is not described as forbidden or permissible. Rather, its cause is what is described as such. If the cause of its emission is permissible, such as enjoying what Allah has made lawful from a wife, then there is no sin in it. But if it is due to an impermissible cause, such as inducing its emission by prolonging glances at what incites lust or by performing a massage, then there is sin in it, and repentance and ghusl (ritual bath) become obligatory.