“Everyone has a light burning for him in the world above, and everyone’s light is unique. When two friends meet, their lights above are united, and out of that union of two lights an angel is born. That angel has the strength to survive for only one year, unless its life is renewed when the friends meet again. But if they are separated for more than a year, the angel begins to languish and eventually wastes away.
“That is why a blessing over the dead is made upon meeting a friend who has not been seen for more than a year, to revive the angel. According to the Talmud two friends who have not seen each other for a year say the blessing: ‘Blessed is He who revives the dead.’”