They are probably not sent by God. E. Dreams serve an emotional problem-solving function. How you feel before bed and how you feel in the morning are systematically related to whom you dream about and what you do in your dreams. Dreaming is an emotional regulatory service, like a thermostat. Dreams update our self-image.
Nightmares indicate that something is boiling over.
Historically violent and sexual nightmares were assumed to be the work of the devil. It shows you pictures not just of someone being short, but of fires and tidal waves. Eventually the brain connects the trauma with all kinds of material in the memory. Click here to view that site. What a relief it is to wake up and realize it was just a dream.