حَدَّثَنَا مُحَمَّدُ بْنُ يَحْيَى، وَإِسْحَاقُ بْنُ مَنْصُورٍ، قَالاَ حَدَّثَنَا عَبْدُ الصَّمَدِ، حَدَّثَنَا شُعْبَةُ، عَنْ قَتَادَةَ، عَنِ الْحَسَنِ، عَنْ سَمُرَةَ، قَالَ قَالَ رَسُولُ اللَّهِ ـ صلى الله عليه وسلم ـ ‏"‏ الْبَيِّعَانِ بِالْخِيَارِ مَا لَمْ يَتَفَرَّقَا ‏"‏ ‏.‏

It was narrated from Samurah that the Messenger of Allah (PBUH) said: "The two parties to a transaction have the choice (of annulling it) so long as they have not yet parted. " Translation Not Available

Book Ref: Sunan Ibn Majah Book 12 Hadith 2183
Web Ref:  Sunan Ibn Majah Vol 3 Book 12 Hadith 2183