Exorcism
In Christianity, exorcism is the practice of casting out demons. In Christian practice the person performing the exorcism, known as an exorcist, is often a member of the Christian Church, or an individual thought to be graced with special powers or skills. The exorcist may use prayers and religious material, such as set formulas, gestures, symbols, icons, amulets, etc. The exorcist often invokes God, Jesus and/or several different angels and archangels to intervene with the exorcism. Protestant Christian exorcists most commonly believe the authority given to them by the Father, Son, and Holy Spirit (the Trinity) is the source of their ability to cast out demons.
Unclean spirit
Exorcism is the most thoroughly attested Jewish magical practice of the Second Temple period. The exorcistic technique of fumigation by incense depends on the aerial conception of the unclean spirit: the occupation of air by odor or smoke (i.e., airborne particulate matter) was supposed to drive off or displace an unclean spirit. Since either body or soul could be unclean, it can be difficult to distinguish exorcism from traditional magico-medical practice in which a personified illness is adjured to depart from the patient's body (for instance, "Flee, Fever!") by means of a charm, spoken or inscribed on an amulet or other ritual object. In some rabbinic literature, demons are viewed as inflicting evil on humans in part through illness and disease, though Mishnah and Tannaitic scholars in Palestine did not view demons as the cause of illness.