Sayyiduna Abdullah bin Amr bin al-As (may Allah be pleased with them both) narrates that the Noble Prophet (peace and blessings be upon him) said: The seller and the buyer both have the option to cancel the transaction before they separate, unless it is an option-based transaction, and it is not permissible for a person to separate out of fear that the transaction will be cancelled.
Hadith Referenceالفتح الربانی / أبواب الشروط فى البيع / 5923
Benefits: … In this hadith, it is considered contrary to good manners (khilaf muruwwah) to quickly change one’s place after a transaction so that the companion does not get the opportunity to return the merchandise; Islamic society does not permit this.
From this blessed hadith, it is understood that trade is not so connected to worldly gain that one should disregard the rights of one’s fellow brother. When the buyer realizes that he can indeed profit from the item, even then he is not permitted to leave the gathering with the intention that the seller’s right to revoke the sale (khiyar al-majlis) will be terminated.