How can the Prophet's saying, "If you gush forth water, then perform ghusl," (meaning if you ejaculate semen) - Sunan An-Nasa'i, Hadith No. 193 - be reconciled with your fatwa that prohibits masturbation?

Masturbation is forbidden (haram). The Hadith of Ali (may Allah be pleased with him): "If you ejaculate water, then perform ghusl (ritual bath)," does not indicate its permissibility. Rather, its purpose is to clarify the obligation of performing ghusl when semen is discharged with force, whether due to intercourse or foreplay, and not to declare the ruling on masturbation.