When your soul manages to escape from your sleeping body, it is never idle; it moves about, contemplating immensity, communicating with heavenly spirits and gaining greater understanding of love, wisdom and truth. When it re-enters your body, it brings with it the memory of all the revelations it has received and attempts to pass them on to your brain. It is these memories that we call dreams.
And it is at night that disciples leave their body and go to join their Master in order to continue learning from him. Here again, when they wake up in the morning, they will not remember exactly what they saw or understood in their sleep, but they will have a sensation of something beautiful and luminous that will stay with them all day long.
For my part, I often talk to you at night, and tell you things that I cannot yet reveal to you on the physical plane, for you would not understand them. Nor, above all, would you know what to do with them. Whereas the truths that I transmit to you by thought are already at work in your subconscious mind, and when you are capable of grasping and using them, they will reveal themselves to you.
Omraam Mikahel Aivanhov,
Izvor Book 228, Looking into the Invisible, Intuition, Clairvoyance, Dreams