Kharija b. as-Salt quoted his paternal uncle as saying:We came to a clan of the Arabs after leaving God's Messenger and they said, “We have been told that you have brought what is good from this man. Have you any medicine, or a charm, for we have a lunatic in chains?" When we replied that we had, they brought a lunatic in chains and I recited Fatihat al-Kitab over him three days morning and evening, collecting my saliva and then spitting it out, and he seemed as if he were set free from a bond. They gave me some payment, but I refused to accept it till I had asked the Prophet. When I did so he said, “Accept it*, for by my life, some accept it for a worthless charm, but you have done so for a genuine one." Ahmad and Abu Dawud transmitted it. * Literally "eat”.
Hadith Referenceمشكوة المصابيح / كتاب البيوع / 2986
Hadith Gradingالألبانی:لم تتمّ دراسته | زبیر علی زئی:إسناده حسن
Hadith Takhrij´تحقيق و تخريج: محدث العصر حافظ زبير على زئي رحمه الله` «إسناده حسن، رواه أحمد (210/5. 211 ح 22179. 22180) و أبو داود (3420)»