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 have not separated, unless it is a transaction with the option (of rescinding)."
Hadith Referenceمسند احمد / مسند المكثرين من الصحابة / 5130
Hadith Gradingحکم دارالسلام:إسناده صحيح ، خ : 2107 ، م : 1531 .