A Christian can have a demon, just as they can have a sickness or disease. Many sickness and diseases for that matter are caused by a demon. Derek Prince (author of They Shall Expel Demons and a Greek scholar) does a good job at pointing out how the Greek does not suggest that a demon can 'own' a person, but rather a person can be under the 'influence' of a demon. read more
Demons actually help promote the teaching that a Christian cannot have a demon, because they gain strength from staying hidden. They can operate in their destructive ways without being challenged! Some may argue that a believer cannot be possessed. read more
A demon cannot dwell in a Christian's spirit because that is where Jesus and the Holy Spirit dwell. It is the other components that make up a human being--the soul (mind, will and emotions) and the body--that are the targets of demonic attack. Demons can dwell in those areas of a Christian's life. read more