There is a great deal of folklore associated with mirrors, including the belief that the soul projects out of the body and into mirrors in the form of reflection. This belief underlies the most widely known mirror superstition; that breaking a mirror brings seven years of bad luck. Many cultures believe that breaking a mirror also breaks the soul of the one who broke it. The soul, angered at being hurt, exacts seven years of bad luck in payment for such carelessness. The Romans attributed the bad luck to their belief that life renews itself every seven years. To break mirror meant breaking one's health, and this could not be remedied for seven years. In some cultures, breaking a mirror was thought to presage a death in the family. This association of mirrors with death is common and stems from the belief that the soul can become trapped in the mirror. For this reason, children were often not allowed to look in a mirror until they were at least one year old. Mirrors were covered during sleep and illness so that the soul, in its wanderings, would not become trapped and unable to return to the body. After a death, mirrors were also covered to prevent the soul of the newly departed from becoming caught in the mirror, delaying its journey to the afterlife.
John's Journal gives more information on mirror folklore:
- Any reflective surface (e.g. water) may be used to catch a glimpse of the future.
- If you perform a certain "wise-woman" ritual while looking in a mirror, you might see your future husband, but also the Grim Reaper.
- At the moment of death, traditionally every mirror in the house is covered, so the soul can't be trapped in it.
- Breaking a mirror is bad luck, because they hold the future.BoM
Sam: Right. I mean there’s a lot of folklore about mirrors-that they reveal all your lies, all your secrets, that they’re a true reflection of your soul, which is why it’s bad luck to break them.
Dean: Right, right. So maybe if you’ve got a secret, I mean like a really nasty one where someone died, then Mary sees it, and punishes you for it.1.05
Mirrors have also been used as means of communication, angels and archangels have been shown to use mirrors or reflective surfaces to communicate with their vessels. The Darkness was also able to communicate with it's younger self, Amara, through the use of a mirror.