Sahih Muslim 1531
Sahih Muslim · Book 21: The Book of Transactions · Affirming that both parties to a transaction have the option (of canceling it) while they are still together
Ibn Umar reported Allah's Messenger (ﷺ) as saying:
حَدَّثَنَا يَحْيَى بْنُ يَحْيَى ، و يَحْيَى بْنُ أَيُّوبَ وَقُتَيْبَةُ وَابْنُ حُجْرٍ قَالَ يَحْيَى بْنُ يَحْيَى أَخْبَرَنَا وَقَالَ الآخَرُونَ، حَدَّثَنَا إِسْمَاعِيلُ بْنُ جَعْفَرٍ ، عَنْ عَبْدِ اللَّهِ بْنِ دِينَارٍ ، أَنَّهُ سَمِعَ ابْنَ، عُمَرَ يَقُولُ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " كُلُّ بَيِّعَيْنِ لاَ بَيْعَ بَيْنَهُمَا حَتَّى يَتَفَرَّقَا إِلاَّ بَيْعُ الْخِيَارِ " .
There is no transaction between two persons entering a transaction until they separate, but only when there is an option to annul it.