Musnad Ahmad 31:786

Yazid narrated to us, Hisham informed us, from Muhammad, from his brother Ma'bad ibn Sirin, from Abu Sa'id al-Khudri, who said: We stopped at a place, and a woman came to us and said: "The leader of the tribe has been stung (by a scorpion/snake), is there any among you who can perform ruqyah (healing incantation)?" A man stood up with her, whom we did not think knew how to perform ruqyah. He went with her and performed ruqyah upon him, and he recovered. They gave him thirty sheep, and I think he said: "And they gave us milk to drink." When he returned to us, we said to him: "Did you know how to perform ruqyah?" He said: "No, I only performed ruqyah upon him with the Opening of the Book (Al-Fatihah)." I said to them: "Do not say anything about it until we come to the Messenger of Allah (ﷺ)." When we arrived, we came to the Messenger of Allah (ﷺ) and I mentioned that to him. He said: "What made him know that it was a ruqyah? Divide (the sheep) and set aside a share for me with you."