From VICE:
A wet dream is basically a freebie: a gift from the orgasm fairy. After all, what could be better than waking up in the night from the sheer force of ejaculation? However, in earlier eras, rather than being the sexual equivalent of a surprise party, they were considered the work of the devil, who squeezed out your semen in a fight for your soul.
There is a Sin Scale, with gangbanging grannies somewhere near the top, and having the occasional wank in the more forgivable spectrum. However, religious folk have always struggled to know where to place the wet dream; there is no act of volition and they are seemingly random. The majority of times I have woken cumming in my sleep I don’t even remember what I was dreaming about, so wouldn’t take kindly to being held responsible for whatever cornucopia of filth was in my sleeping head.
