There are no earth-bound 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 when they are alive on the earth… But the good souls are given eternal life and sometimes God permits their thoughts to reach the earth to help the people.
(‘Abdu’l-Bahá, Daily Lessons, Received at ‘Akká, 1979 ed., pp. 35-36)
There is no power exercised over the people by those evil souls that have passed away. Good is stronger than evil and even when alive they had very little power. How much less have they after they are dead, and besides they are nowhere near this planet.
(‘Abdu’l-Bahá, Daily Lessons, Received at ‘Akká, 1979 ed., pp. 43-44)