Medicine (Kitab Al-Tibb)
Dawud :: Book 28 : Hadith 3887
Narrated Alaqah ibn Sahar at-Tamimi:
Alaqah came to the Apostle of Allah (may peace be upon him) and embraced Islam. He then came back from him and passed some people who had a lunatic fettered in chains.
His people said: We are told that your companion has brought some good. Have you something with which you can cure him? I then recited Surat al-Fatihah and he was cured. They gave me one hundred sheep. I then came to the Apostle of Allah (peace_be_upon_him) and informed him of it.
He asked: Is it only this? The narrator, Musaddad, said in his other version: Did you say anything other than this? I said: No. He said: Take it, for by my life, some accept if for a worthless chain, but you have done so for a genuine one.