Does halacha require Jews to rinse their hands when they wake up because of some "contamination" that happened while they were asleep?
If so what exactly was that contamination?
One reason why we wash our hands in the morning is brought down in the Kitzur Shulchan Aruch (2:1). When we go to sleep, our neshama leaves our body and a ruach tumah (unclean spirit) rests upon us. When we wake up, the ruach tumah leaves the rest of the body and dwells in the fingers. When we wash our hands, the ruach tumah leaves completely, having no where to go.