In Jewish tradition, a flame symbolized the soul of man reaching ever upward.  This is suggested by the verse in Proverbs 20:27, "The soul of man is the lamp of the Lord."  By lighting a candle and keeping it burning throughout the Shiva period, it is believed that the soul of the departed is aided in its journey heavenward.  

     When the patriarch Rabbi Judah the Prince (135-220 C. E.), editor of the Mishna, was on his deathbed, he called for his sons and instructed them that "the light (which he used during his lifetime) shall continue to burn in its usual place."  This, say some commentaries, is the basis for the custom that a light be kindled in the house of mourning.  

    Today, a memorial or Shiva candle is kept burning for the duration of Shiva.  Some Sephardim, however, continue to keep one burning throughout the entire first year of mourning.