It is narrated from Sayyiduna Hakim bin Hizam (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: The buyer and the seller have the option (to cancel the transaction) as long as they have not separated. If both act truthfully in the transaction and make everything clear, they will be blessed in their trade; but if they lie and conceal (defects, etc.), the blessing will be taken away from their trade.