Sahih al Bukhari 2113
Sales and Trade
حَدَّثَنَا مُحَمَّدُ بْنُ يُوسُفَ، حَدَّثَنَا سُفْيَانُ، عَنْ عَبْدِ اللَّهِ بْنِ دِينَارٍ، عَنِ ابْنِ عُمَرَ ـ رضى الله عنهما ـ عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ " كُلُّ بَيِّعَيْنِ لاَ بَيْعَ بَيْنَهُمَا حَتَّى يَتَفَرَّقَا، إِلاَّ بَيْعَ الْخِيَارِ ".
Narrated Ibn `Umar:The Prophet (ﷺ) said, "No deal is settled and finalized unless the buyer and the seller separate, except if the deal is optional (whereby the validity of the bargain depends on the stipulations agreed upon)
Text from the public-domain hadith-api dataset. Numbering follows that dataset and can differ by a few from some printed editions — check the wording, not only the number.