Sunan an-Nasa'i, Book 44, Hadith 17 (In-Book) ⓘ
It was narrated from Malik, from Nafi from'Abdullah bin 'Umar that the Messenger of Allah said: "The two parties to a transaction both have the choice so long as they both chosen to conclude the transaction." (Sahih )
أَخْبَرَنَا مُحَمَّدُ بْنُ سَلَمَةَ، وَالْحَارِثُ بْنُ مِسْكِينٍ، قِرَاءَةً عَلَيْهِ وَأَنَا أَسْمَعُ، - وَاللَّفْظُ لَهُ - عَنِ ابْنِ الْقَاسِمِ، قَالَ حَدَّثَنِي مَالِكٌ، عَنْ نَافِعٍ، عَنْ عَبْدِ اللَّهِ بْنِ عُمَرَ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ " الْمُتَبَايِعَانِ كُلُّ وَاحِدٍ مِنْهُمَا بِالْخِيَارِ عَلَى صَاحِبِهِ مَا لَمْ يَفْتَرِقَا إِلاَّ بَيْعَ الْخِيَارِ " .
also referenced under: Hadith 4465 (Reference) & Volume 5, Book 44, Hadith 4470 (DarusSalam)