Mkhld bin Yazid al-Quraishi مخلد بن يزيد القرشي الحراني · 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 )

"The messenger of Allah forbade two kinds of transactions: Mulamash and Mumabadha."

"The Messenger of Allah granted a concession allowing 'Araya sales for fresh dates and for dried dates, but he did not allow anything other than that."