Abdullah bin 'Awn bin Artaban عبد الله بن عون بن أرطبان الخزار · 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 selling gold for gold, silver for silver, dates for dates, wheat for wheat, barley for barley"- one of them said: "salt for salt," but the other did not say it-"unless it was equal amount for equal amount, like for like." One of them said: "Whoever gives more or takes more has engaged in Riba," but he other one did not say it. "And he commanded us to sell gold for silver and silver for gold,…