Hadith
أَخْبَرَنِي مُحَمَّدُ بْنُ إِسْمَاعِيلَ بْنِ إِبْرَاهِيمَ، قَالَ حَدَّثَنَا يَزِيدُ، قَالَ أَنْبَأَنَا هَمَّامٌ، عَنْ قَتَادَةَ، عَنِ الْحَسَنِ، عَنْ سَمُرَةَ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " الْبَيِّعَانِ بِالْخِيَارِ مَا لَمْ يَتَفَرَّقَا وَيَأْخُذْ أَحَدُهُمَا مَا رَضِيَ مِنْ صَاحِبِهِ أَوْ هَوِيَ " .
It was narrated from Al- Hasan from Samurah, who said:"The Messenger of Allah said;" Two traders have the choice as long as they have not separated, or until they reach a deal that suits both of th4em or that is satisfactory (to both)
Da'if · Abu Ghuddah
Sunan an-Nasa'i 4482 ·Book 44, Hadith 34·Also available on sunnah.com·