Sulaiman al-A'mash الأعمش / سليمان بن مهران · The Chapters on Business Transactions

"We were sitting in a gathering, and the Prophet (ﷺ) came with traces of water on his head. One of us said to him: 'We see that you are of good cheer today.' He said: 'Yes, praise is to Allah.' Then he spoke to the people about being rich. He said: 'There is nothing wrong with being rich for one who has piety, but good health for one who has piety is better than riches, and being of good cheer…

"A man is not to undersell his brother, nor is he to fry to outhaggle his brother."

the Prophet (ﷺ) forbade the Najsh.

”The two parties to a transaction have the choice (of annulling it) so long as they have not yet parted."

"The Messenger of Allah (ﷺ) bought a load of fodder from a Bedouin man. When the transaction was concluded, the Messenger of Allah (ﷺ) said: 'Choose (either to go ahead or to cancel the transaction).' The Bedouin said: 'May Allah grant you a long life of good transaction!"'