Abdullah bin Abbas reported,

A group of the companions of the Messenger of Allah ﷺ passed by a watering place where there was a man who had been stung, or bitten by a snake. A man from the people of that watering place came up to them and asked, "Is there anyone among you who can perform a healing recitation? There is a man at the water who has been stung, or bitten."So one of them went with him and recited al-Fatihah over a flock of sheep, and the man recovered. He brought the sheep back to his companions, but they disliked what he had done and said, "Did you take payment for reciting the Book of Allah?"When they reached Medina, they said, "Messenger of Allah, he took payment for reciting the Book of Allah."The Messenger of Allah said, "The most deserving thing for which you can take payment is the Book of Allah."

عن ابن عباس

أن نفرا من أصحاب رسول الله ﷺ مروا بماء فيهم لديغ- أو سليم-، فعرض لهم رجل من أهل الماء، فقال: هل فيكم من راق؛ إن في الماء رجلا لديغا- أو سليما-؟ فانطلق رجل منهم، فقرأ بفاتحة الكتاب على شاء، فبرأ، فجاء بالشاء إلى أصحابه، فكرهوا ذلك، وقالوا: أخذت على كتاب الله أجرا؟ حتى قدموا المدينة، فقالوا: يا رسول الله، أخذ على كتاب الله أجرا؟ فقال عليه السلام: إن أحق ما أخذتم عليه أجرا كتاب الله.