Likutei Halakhot/Orach Chayim/The Morning Hand Washing
“ Therefore, God imprinted the instinct in man that when the mind is too confused and tired that one falls asleep, closing one's eyes and submerging the mind, completely letting go of one's consciousness and intellect. This is the submergence, surrendering oneself into the Absolute Good, where all confusions, including all judgments, troubles, pains and obstacles, disappear and are all submerged into the ultimate purpose. This is why sleep is innate to man and to all creatures. ”
