And the soul that turneth after such as have familiar spirits, and after wizards, to go a whoring after them, I will even set my face against that soul, and will cut him off from among his people. (Leviticus 20:6 KJV)
The term “familiar spirits” is used in the Bible to describe those who use information gained through demons on a regular basis. In those days, these people would have included psychics, tarot card readers, palm readers, witch doctors, along with wizards. Is it harmless to get your palm read? Or to go to a tarot card reader?
According to the above scripture, there is a stiff penalty for associating with spirits who are not from God: He turns His face from us. This means we will lose God's favor and His presence. If you were cut off from your people, you couldn't go to the temple to pray or to offer sacrifices. For Christians this means that your prayers will be hindered if you listen to familiar spirits!
Besides this direct reference, many Christians use the term “familiar spirit” to refer to a particular aspect of Satan’s network. We know that Satan frequently tries to imitate God. Most of us are aware that we have a “guardian” angel assigned to us (Matthew 18:10, Hebrews 1:14). Satan isn’t omnipresent. He can only be in one place at one time. The Devil assigns demons to humans to keep an eye on them and to harass them. Sometimes Christians refer to these minions as “familiar spirits” because they know us and have often been passed down through our family line.
Many spirits can speak to us which are not from God:
But even if we or an angel from heaven should preach to you a gospel contrary to and different from that which we preached to you, let him be accursed… (Galatians 1:8 AMPC)