Abdullah b. 'Umar (Allah be pleased with them) reported Allah's Messenger (ﷺ) as saying: When two persons enter into a transac. tion, each one of them has the right to annul it so long as they are not separated, or their transaction gives one another (as a condition) the right of annulling, and if their transaction, has the right of annulling it the transaction becomes binding. Ibn Abi Umar made this addition that whenever he (Ibn Umar) entered into a transaction with a person with the intention of not breaking it, he walked a while and then returned to him.
Source: sunnah.com
Other translations
Arabic
وَحَدَّثَنِي زُهَيْرُ بْنُ حَرْبٍ، وَابْنُ أَبِي عُمَرَ، كِلاَهُمَا عَنْ سُفْيَانَ، - قَالَ زُهَيْرٌ حَدَّثَنَا سُفْيَانُ بْنُ عُيَيْنَةَ، - عَنِ ابْنِ جُرَيْجٍ، قَالَ أَمْلَى عَلَىَّ نَافِعٌ سَمِعَ عَبْدَ اللَّهِ بْنَ عُمَرَ، يَقُولُ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " إِذَا تَبَايَعَ الْمُتَبَايِعَانِ بِالْبَيْعِ فَكُلُّ وَاحِدٍ مِنْهُمَا بِالْخِيَارِ مِنْ بَيْعِهِ مَا لَمْ يَتَفَرَّقَا أَوْ يَكُونُ بَيْعُهُمَا عَنْ خِيَارٍ فَإِذَا كَانَ بَيْعُهُمَا عَنْ خِيَارٍ فَقَدْ وَجَبَ " . زَادَ ابْنُ أَبِي عُمَرَ فِي رِوَايَتِهِ قَالَ نَافِعٌ فَكَانَ إِذَا بَايَعَ رَجُلاً فَأَرَادَ أَنْ لاَ يُقِيلَهُ قَامَ فَمَشَى هُنَيَّةً ثُمَّ رَجَعَ إِلَيْهِ .
sunnah.com