It is narrated from Sayyiduna Ibn Umar (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) said: "The seller and the buyer have the option (to cancel the transaction) as long as they do not separate, or until they make a sale with the option (of choice)."
Hadith Referenceمسند احمد / مسند المكثرين من الصحابة / 5158
Hadith Gradingحکم دارالسلام:إسناده صحيح ، خ : 2107 ، م : 1531 .