Does the fast become invalid if the fasting person wakes up from sleep while semen is being discharged during a wet dream, and then intentionally helps the semen to exit?

The emission of semen due to a wet dream does not invalidate the fast. If its emission is due to thinking and imagining, it does not break the fast according to the majority of scholars, but it is more prudent to make up that day. However, if the emission of semen is caused by an intentional act while awake, the fasting person must make up that day along with repentance, but expiation is not required of him.