Hadith #3420 (Sunan Abi Dawud)
Book: Wages (Kitab Al-Ijarah)
Narrator(s): Aban bin Tghlb أبان بن تغلب, al-Sa'ib bin Yazid bin Akht Namr, Ibrahim bin 'Abdullah bin Qariz إبراهيم بن عبد الله بن قارظ, Musa bin Isma'il al-Munqari al-Tabudhaki موسى بن إسماعيل المنقري - لتبوذكي, Rafi' bin Khadij bin Rafi', Yahya bin Sa'id bin Farroukh al-Qatan يحيى بن سعيد بن فروخ القطان
Grade: Sahih

You have brought what is good from this man. Then they brought a lunatic in chains. He recited Surat al-Fatihah over him three days, morning and evening. When he finished, he collected his saliva and then spat it out, (he felt relief) as if he were set free from a bond. They gave him something (as wages). He then came to the Prophet (ﷺ) and mentioned it to him. The Messenger of Allah (ﷺ) said: Accept it, for by my life, some accept it for a worthless charm, but you have done so far a genuine one.

Source: https://parallelquran.com/hadith/sunan-abi-dawud-3420/