Musnad Ahmad 1153:9

Hushaym narrated to us, he said: Mughirah informed us, from Ibrahim, from al-Aswad, from Aisha: "That the Messenger of Allah, peace and blessings of Allah be upon him, granted a concession to a household of the Ansar regarding ruqyah (incantation), for every possessor of a venomous sting."