Netilas Yadayim and Ruach Rah

When a person sleeps, the highest part of his soul goes through a spiritual process. In a manner of speaking, it leaves the rest of the soul and the body, and interacts with the Upper Worlds. The particular nature of the interaction, and its results, if any, depend on numerous factors, and generally do not really concern us in any tangible way.

When the High Soul leaves the body, it leaves a spiritual vacuum in its place, which causes an unclean spiritual experience for the body. Our souls are what give us life, what separates us from animals, and what makes us holy. When our Neshamos leave us, we go down a little, and we are that much closer to death, to animals, and to unholiness. Even after the Neshamah returns, the effects of its absence remain, to an extent. That is the Ruach Ra'ah.

There is still some residue spiritual uncleanliness that remains in the fingers, which has to be removed through a process called Negel Vasser, or Neteilas Yadayim in Hebrew.

This is done by rinsing the hands with water poured from a cup - from one hand on to the next, and then vice versa - and twice again, so that each hand had was rinsed three times.

Before Negel Vasser, you may not touch any food, and if you do, that food should not be eaten before it itself is rinsed.

Negel Vasser should be performed immediately upon awakening.