Abu Sa’id al-Khudri and Ibn Abbas (RA) reported that a number of the Prophet's (Peace and Blessing upon Him) companions were on a journey. They stopped one night by the dwellings of a bedouin tribe who refused to host them and give them food.
The chief of that tribe was then stung (by a snake or scorpion). His people tried everything possible to treat him, but to no avail. One of them suggested to seek help from the travellers. When they came to them, one of them said, "By Allah, I can perform ruqyah; but you have refused to host us. So I would not perform the ruqyah until you pledge to give us an offering."
They agreed to give them a flock of thirty sheep, and the companion started blowing (with light spit) on the stung man's sting and reading al-Fatiha. He was immediately cured, like one who was tied and then set free. He stood and walked as if nothing happened to him, and they gave them their pledged offering.
Some of the companions said, "Let us divide this flock among us." Others said, "No, you may not take any pay for reading Allah's Book! Let us not divide the goats until we reach the Prophet (Peace and Blessing upon Him), tell him what happened, and see what he commands us."
When they reached al-Madinah, they came to the Prophet (Peace and Blessing upon Him) and told him what happened. He said (approvingly):
‘How did you know that it (al-Fatiha) is a ruqyah? You have done well! And indeed, the best thing to be paid for is Allah's Book*. So, divide it among you; and allot a share for me.’ Al-Bukhari, Muslim, and others.
(*One may not be paid for praying or reading Qur’an, because these are acts of worship that should be done purely for Allah ('Azza wa Jalla). However, it is permissible to be paid a compensation for the time or effort that one sometimes puts into matters associated with these acts of worship in order to serve the Muslim community. For example, a regular imam in a masjid should be compensated for devoting his time to that position, otherwise he would have to work in a profession that would prevent him from fulfilling all of the services needed from him. Furthermore, based on this hadith, some scholars conclude that it is also permissible to be paid for a benefit that reaches others because of one's reading Qur’an.)