'Abdu'l-Baha answered, "There are no earthbound souls.
When the souls that are not good die, they go entirely away from this earth and
so cannot influence anyone. They are spiritually dead. Their thoughts can have
influence only while they are alive on the earth. Caiaphas had great influence
during his life, but as soon as he died, his influence ceased. It was of this
kind that Christ said, 'Let the dead bury their dead.' But the good souls are
given eternal life, and sometimes God permits their thoughts to reach the earth
to help the people.” - 'Abdu'l-Baha (From a conversation, ‘Daily Lessons
Received at Akka January 1908”, by Helen Goodall and Ella Goodall Cooper)