Sahih al-Bukhari 2113
Sahih al-Bukhari · Book 34: Sales and Trade · If the seller has the option of cancelling the bargain
Narrated Ibn `Umar:
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 " .
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).