The prohibition on masturbation is accompanied by a combination of draconian deterrent and preventative measures.
Written By Prof. Gideon Aran
Throughout the day boys at kindergarten are berated should their hand accidentally touch that shameful area, and before going to sleep their hands are placed outside the blankets, which are pulled up to the neck and smoothed down tightly around the chest, in case the hands should wander towards the penis.
Supervision over the teenaged body continues throughout the night. Anyone sleeping on their stomach is woken up to change their position so as to prevent their penis rubbing against the mattress and causing unintentional ejaculation.
In any event, the first thing to do upon waking up in the morning is to dip their hands in a bowl of water placed by their bed, because one may have touched the penis while dreaming thus making himself impure. For similar reasons mothers avoid bodily contact with sons whom they no longer breastfeed.
Taken from “Denial Does Not Make The Haredi Body Go Away Ethnography of a Disappearing (?) Jewish Phenomenon”, By Prof. Gideon Aran.