مُسْنَدُ أَحْمَدَ
Musnad Ahmad 4239
Musnad of Abdullah bin Mas'ood
‘Ata' bin as-Sa’ib said: I came to Abu ‘Abdur-Rahman when he was cauterizing a boy and I said: Are you cauterizing him? He said: Yes, it is the medicine of the Arabs. 'Abdullah bin Mas'ood said: The Messenger of Allah (ﷺ) said: “Allah, may He be glorified and exalted, did not send down any disease but He sent with it a remedy. Those of you who do not know it do not know it, and those of you who do know it know it."
Musnad Ahmad 4267Saheeh because of corroborating evidence]