Abu Dawud
Medicine
Book Number: 022 / Hadith Number: 3887
Narated By 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 (pbuh) 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.