Amr bin Dinar عمرو بن دينار الأثرم الجمحي · The Book of Financial Transactions

"The Messenger of Allah said: 'The two parties to a transaction both have the choice so long as they have not separated, unless they have both chosen to conclude they transaction. If they have both chosen to conclude the transaction, then the transaction is binding." (Sahih )

"Abu Al-Mutawakkil passed by them in the market and some people, including me, stood up to greet him. We said: 'We have come to you to ask you about transactions.' He said: 'I heard a man say to Abu Saeed Al-Khudri': 'Is there anyone between you and the Messenger of Allah (in the chain of narrators) apart from Abu Saeed Al-Khudri? He said: 'There is no one else between him and I. He said: Gold for gold, silver for silver,…

"I heard the Messenger of Allah say: 'Gold, equal amount."' (One of the narrators) Yaqub did not mention: "Equal amount." Muawiyah said: "This does not mean anything." 'Ubadah said; "By Allah I do not care if I am in a land where Muawiyah is not present. I bear witness that I heard the Messenger of Allah say that."

"My eyes saw and my ears heard the Messenger of Allah. And he mentioned the prohibition of (selling) gold for gold and silver for silver, unless it is equal amounts, like for like. And do not sell it in return for something to be paid later, and do not differentiate."

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"The Messenger of Allah died when his shield was in pledge with a Jew for thirty Sa's of barley for his family

a man from among the Ansar who was called Abu (Madhkur) stated that a slave of his who was called Ya'qub was to be set free after he died, and he did not own any other property apart from him. The Messenger of Allah called for him (the slave) to be brought and he said: "Who will buy him?" Nu'aim bin 'Abdullah bought him for eight hundred dirhams, and he gave it to him and said: "If one of you…