Sunan an-Nasai Book 44, Hadith 4649

أَخْبَرَنِي إِبْرَاهِيمُ بْنُ الْحَسَنِ، وَيُوسُفُ بْنُ سَعِيدٍ، وَعَبْدُ الرَّحْمَنِ بْنُ خَالِدٍ، - وَاللَّفْظُ لإِبْرَاهِيمَ - قَالُوا حَدَّثَنَا حَجَّاجٌ، قَالَ قَالَ ابْنُ جُرَيْجٍ أَخْبَرَنِي إِسْمَاعِيلُ بْنُ أُمَيَّةَ، عَنْ عَبْدِ الْمَلِكِ بْنِ عُبَيْدٍ، قَالَ حَضَرْنَا أَبَا عُبَيْدَةَ بْنَ عَبْدِ اللَّهِ بْنِ مَسْعُودٍ أَتَاهُ رَجُلاَنِ تَبَايَعَا سِلْعَةً فَقَالَ أَحَدُهُمَا أَخَذْتُهَا بِكَذَا وَبِكَذَا ‏.‏ وَقَالَ هَذَا بِعْتُهَا بِكَذَا وَكَذَا ‏.‏ فَقَالَ أَبُو عُبَيْدَةَ أُتِيَ ابْنُ مَسْعُودٍ فِي مِثْلِ هَذَا فَقَالَ حَضَرْتُ رَسُولَ اللَّهِ صلى الله عليه وسلم أُتِيَ بِمِثْلِ هَذَا فَأَمَرَ الْبَائِعَ أَنْ يَسْتَحْلِفَ ثُمَّ يَخْتَارَ الْمُبْتَاعُ فَإِنْ شَاءَ أَخَذَ وَإِنْ شَاءَ تَرَكَ ‏.‏

It was narrated that 'Abdul-Malik bin'Ubaid said:"We were with Abu 'Ubaidah bin 'Abdullah bin Mas'ud when two men who were involved in a transaction came to him. One of them said: 'I bought it for such and such', and the other said; 'I sold it to him for such and such,' Abu 'Ubaidah said" 'something like this was brought to Ibn Masud, and he said; I was with something like this was brought to him. He told the seller to swear an oath, them he gave the purchaser the choice; If he wished, he could buy it, and if he wished he could cancel (the transaction)