Abu Bakr bin 'Ayyash al-Asadi أبو بكر بن عياش بن سالم الأسدي · The Chapters on Business Transactions

"The Messenger of Allah (ﷺ) sent us, thirty horsemen, on a military campaign. We camped near some people and asked them for hospitality but they refused. Then their leader was stung by a scorpion and they said: 'Is there anyone among you who can recite Ruqyah for a scorpion sting?' I said: 'Yes, I can, but I will not recite Ruqyah for him until you give us some sheep.' They said: 'We will give you thirty sheep.' So we accepted…

"Do not meet the traders on the way, and whoever meets any of them and buys from him, the vendor has the choice of annulling the transaction when he comes to the marketplace.''