It is narrated from Sayyiduna Hakim bin Hizam that the Prophet (peace and blessings be upon him) said: The seller and the buyer (the one who sells and the one who buys) have the option (to cancel the transaction) as long as they do not separate. Abdullah says: I also found this addition in my father's book, that if both of them speak the truth and clarify everything, then they will be blessed in their transaction, and if they lie and conceal something, then the blessing of their transaction will be taken away from them.