Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) narrates this statement of the Noble Prophet (peace and blessings be upon him): "A transaction between two people engaged in buying and selling is not complete until they separate from each other, except in the case of a transaction in which there is an option (to cancel later); its ruling is different."
Hadith Referenceصحیح ابن حبان / كتاب البيوع / 4913
Hadith Gradingفضيلة الشيخ الإمام محمد ناصر الدين الألبانيصحيح - «الإرواء» (5/ 155)، «البيوع»: ق.فضيلة الشيخ العلّامة شُعيب الأرناؤوطإسناده صحيح على شرط الشيخين