What is the ruling on retaining semen during a wet dream, and what is the ruling on the fluid that is discharged thereafter, and does it necessitate ghusl?

Scholars have differed regarding the obligation of ghusl for one who withholds semen after it has moved and reached the penis but has not exited. Some scholars, such as the Maliki and Hanbali schools, obligate ghusl in this case. Others, such as the Shafi'i school, do not obligate it unless the semen actually exits. As for the fluid that has actually exited, and one is certain that it is not semen, ghusl is not obligatory; rather, washing the penis suffices. It should be noted that what exits with desire is often either semen or madhiy (pre-seminal fluid).