It is narrated from Sayyiduna Ibn Mas'ud (may Allah be pleased with him) that I heard the Prophet (peace and blessings of Allah be upon him) say: "If the seller and the buyer disagree and the goods are still present as they were, then the statement of the seller will be accepted; otherwise, both should take back their respective things."
Hadith Referenceمسند احمد / مسند المكثرين من الصحابة / 4446
Hadith Gradingحکم دارالسلام:حسن، وهذا إسناد ضعيف لانقطاعه، القاسم لم يدرك جده ابن مسعود.