Muhammad bin 'Abdul A'la محمد بن عبد الأعلى · The Book of Financial Transactions

a man told the Messenger of Allah that he was always being cheated. The Messenger of Allah said to him: "When you make a deal, say: There is no intention of cheating" So, whenever the man engages in a deal he says, 'There is no intention of cheating." "(Sahih )

the Messenger of Allah forbade artificially inflating prices, meeting traders on the way, and for a town-dweller to sell for a desert-dweller." (Sahih )

"No tow-dweller should sell for desert-dweller, no man should outbid his brother; and no woman should ask for her sister (in faith) to be divorced so as to turn over what is in her bowl (deprive her of her share of maintenance)"

"The Messenger of Allah forbade two kinds of garments and two kinds of transactions. As for the two kinds of transactions, they are Mulamash and Munabadhaha. Munabadha is when a man says, 'I throw this garment, and the transaction becomes binding, and Mulamasah is when a man touches it with his had, without spreading it out and checking it, and once he touches it, the transaction becomes binding."

"There is no Riba except in credit.'

"The Messenger of Allah forbade lending on the condition of a sale, selling what you do not have, and profiting on what you do not possess.

"If a woman is married off by two guardians, then the first marriage is the one that counts, and if a man sells something to two men, it belongs to the first one."