Abu Sulayman (al-Khattabi) (may Allah have mercy on him) said: "Nushrah is a type of ruqyah and treatment by which a person is treated who is thought to be touched by the jinn (possessed). It is said that it is called nushrah because by it (the healer) unties (the illness) from him, that is, he removes from him the illness that has permeated him."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الضحايا / Q19613