Soul and Sleep

 Zohar (Bereishis 010b) At the beginning of the day, when a man rises in the morning, it is his duty to bless his Master as soon as he opens his eyes. The pious men of old used to have by them a cup of water, and when they awoke in the night they washed their hands and rose and occupied themselves in the study of the Torah, having first pronounced the appropriate blessing. When the cock crows it is precisely midnight, and at that moment the Holy One, blessed be He, is to be found in company with the righteous in the Garden of Eden. It is therefore proper then to pronounce the benediction and study the Torah; but one may not pronounce the benediction with unclean hands. So, too, at any time that one rises up from his sleep. For whilst a man is asleep his soul departs from him and an impure spirit comes forth and settles on his hands and defiles them: hence one may not pronounce a blessing without first washing them.