What is the ruling on masturbating while holding back semen, and is ghusl then required, and is the prayer valid if one only performs wudu?

Masturbation is forbidden, and it is obligatory to repent immediately and resolve not to return to it, for Allah is more deserving of shyness from. As for performing ghusl after holding back semen, the jurists have differed in their opinions, but performing ghusl is more cautious and absolves one's responsibility.