Answer: An ordinary dream is no different than other states that a person experiences, except that at this time the brain is detached from the perception of our world and of the upper world, and is involved with the correct storage of information that is gathered in a state of disorder within it.
Question: Is immersion in a dream or sleep more or less an egoistic state?
Answer: No more and no less. It is simply a mundane state in which the brain organizes itself. It is really involved in a lot of work during sleep, and it is necessary to allow the opportunity for it.
Question: Does the wisdom of Kabbalah explain why a person spends around a third of his life asleep?
Answer: Certainly, a lot is written about sleep in the wisdom of Kabbalah. A state of sleep is divided into two parts: the physical and the spiritual. The wisdom of Kabbalah examines how this state happens in us, and from what spiritual source it is derived. After all, everything in our world has a spiritual root.
Kabbalah investigates the roots of everything that happens on Earth. The spiritual source of dreaming is the ejection of Light from the Kli, from the desire, so basically only a small amount of Light remains in it. Then the Kli is found in a passive state called a “dream,” which is “a sixtieth part” of death.
From the Kabbalah Lesson in Russian 1/17/16