The most common objection I hear as a counselor/deliverance minister against the idea of a believer having a demon is 2 Cor 6:14.
Do not be yoked together with unbelievers. For what do righteousness and wickedness have in common? Or what fellowship can light have with darkness.
Reading this verse in context, which is extremely important bible exegesis, Paul is actually lecturing the saints about believers marrying (or I believe being in business with) unbelievers.
Another misconception is that a person who is demon possessed is owned and fully operated by a demon. This is not true either. The bible makes it clear that as believers we are “owned” by or “possessed” by God. We become children of God, adopted into his family, grafted into the vine, as it were. A person can be perfectly sane, be saved and yet still have a demon. The word possessed in the NT Greek actually means to be under the power of a demon or to have a demon. This is like being under the power or influence of alcohol, the more you drink, the more you come under its power. Same is true with demonic bondage, the more bondage you are in, the more you will come under that demon’s influence or power.
Christians Cannot Be Demon-Possessed
Saying that a Christian can be possessed, is like saying that termites own the house they are destroying. A Christian can have one or more demons and be in bondage (oppressed or influenced) but it does not mean that the person is owned by the demons.
Some demons cause blindness, others cause deafness, others cause madness (mental illness), others cause fear and depression (King Saul), others cause epilepsy (Matthew 17:15-21), and so forth. Therefore, if a person is under the power of a spirit of blindness, they won’t see (Matthew 12:22), if they are under the power of a spirit of infirmity, they will have some sort of physical infirmity (Luke 13:11), if they are under the power of a spirit of fear, they will be fearful, or if they are under the power of a spirit of anger, they will have uncontrollable anger.
Demons can invade the soul and body of a believer (if given the ‘rights’ of course), but not the spirit (the real you), because the spirit (which is born again (John 3:6-7)belongs to the Lord). The soul is where your thoughts, emotions, and thinking is done. Demons can cause fear, depression, lust, uncontrollable anger, and other iniquities in the soul, and sickness and diseases in the body. A person must be delivered of these demons, either sovereignly or by being ministered to, in order to gain lasting freedom!