Mishkat al-Masabih, hadith 2761

وَعَنْ عَبْدِ اللَّهِ بْنِ مَسْعُودٍ قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: «إِذَا اخْتَلَفَ الْبَيِّعَانِ فَالْقَوْلُ قَوْلُ الْبَائِعِ وَالْمُبْتَاعُ بِالْخِيَارِ» . رَوَاهُ التِّرْمِذِيُّ وَفِي رِوَايَةِ ابْنِ مَاجَهْ وَالدَّارِمِيِّ قَالَ: «الْبَيِّعَانِ إِذَا اخْتَلَفَا وَالْمَبِيعُ قَائِمٌ بِعَيْنِهِ وَلَيْسَ بَيْنَهُمَا بَيِّنَةٌ فَالْقَوْلُ مَا قَالَ الْبَائِعُ أَو يترادان البيع»

‘Abdallah b. Mas'ud reported God’s Messenger as saying, “When two people who are arranging a business transaction disagree the decision rests with the seller, but the buyer has the right to choose whether he will confirm this*.” Tirmidhi transmitted it. In the version of Ibn Majah and Darimi he said, “When two people who are arranging a business transaction disagree, the commodity being present and is neither being able to prove his case, the decision rests with the seller, or they may both reject the transaction.” * The seller swears an oath to the effect that he is right. The buyer may either agree or swear in an oath that he is right. In the latter instance the qadi cancels the deal.