The Zohar on the mitzva of washing the hands upon awakening:

“…There is no human who does not taste the taste of death at night and consequently an impure spirit (rucha mesa’ava) descends upon him. Why does this happen? When the holy soul leaves the human body … an impure spirit descends upon the body. When the soul is returned to the body and the impurity is removed, it remains upon his hands, and cannot be removed until the human washes them, thereby being sanctified…”

…One should not recite a berakha until this impurity is removed. Furthermore, the Zohar asserts that one should not walk four amot (cubits) before washing one’s hands, and describes the proper means of removing this impurity: One takes the vessel containing the water in one’s right hand and passes it to the left hand. One then washes the right and left hands in sequence, three times, based upon the kabbalistic tension between the sefirot of din and chesed, represented by the left and right hands, respectively.”