Musnad Ahmad 26:717

I read to my father: Ali ibn Asim narrated to us, Ata’ ibn al-Sa’ib informed me, he said: I came to Abu Abd al-Rahman, and he was cauterizing a young boy. I said: "Are you cauterizing him?" He said: "Yes, it is the medicine of the Arabs." Abdullah ibn Mas’ud said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Indeed, Allah the Almighty did not send down a disease except that He also sent down with it a cure; those of you who were ignorant of it were ignorant, and those of you who knew it knew it."