Both parties in a business transaction have the right to annul it so long as they have not separated; except in transactions which have been made subject to the right of parties to annul them.  

أَنَّ رَسُولَ اللَّهِ ﷺ قَالَ الْبَيِّعَانِ كُلُّ وَاحِدٍ مِنْهُمَا بِالْخِيَارِ عَلَى صَاحِبِهِ مَا لَمْ يَتَفَرَّقَا إِلاَّ بَيْعَ الْخِيَارِ  

This hadith has been narrated on the authority of Ibn 'Umar (Allah be pleased with them) through another chain of transmitters.  

عَنِ النَّبِيِّ ﷺ ح وَحَدَّثَنِي زُهَيْرُ بْنُ حَرْبٍ وَعَلِيُّ بْنُ حُجْرٍ قَالاَ حَدَّثَنَا إِسْمَاعِيلُ ح وَحَدَّثَنَا أَبُو الرَّبِيعِ وَأَبُو كَامِلٍ قَالاَ حَدَّثَنَا حَمَّادٌ وَهُوَ ابْنُ زَيْدٍ جَمِيعًا عَنْ أَيُّوبَ عَنْ نَافِعٍ عَنِ ابْنِ عُمَرَ عَنِ النَّبِيِّ ﷺ ح وَحَدَّثَنَا ابْنُ الْمُثَنَّى وَابْنُ أَبِي عُمَرَ قَالاَ حَدَّثَنَا عَبْدُ الْوَهَّابِ قَالَ سَمِعْتُ يَحْيَى بْنُ سَعِيدٍ ح وَحَدَّثَنَا ابْنُ رَافِعٍ حَدَّثَنَا ابْنُ أَبِي فُدَيْكٍ أَخْبَرَنَا الضَّحَّاكُ كِلاَهُمَا عَنْ نَافِعٍ عَنِ ابْنِ عُمَرَ عَنِ النَّبِيِّ ﷺ نَحْوَ حَدِيثِ مَالِكٍ عَنْ نَافِعٍ  

When two persons enter into a transaction, each of them has the right to annul it so long as they are not separated and are together (at the place of transaction) ; or if one gives the other the right (to annul the transaction) But if one gives the other the option, the transaction is made on this condition (i. e. one has the right to annul the transaction), it becomes binding. And if they are separated after they have made the bargain and none of them annulled it, even then the transaction is binding.  

عَنْ رَسُولِ اللَّهِ ﷺ أَنَّهُ قَالَ إِذَا تَبَايَعَ الرَّجُلاَنِ فَكُلُّ وَاحِدٍ مِنْهُمَا بِالْخِيَارِ مَا لَمْ يَتَفَرَّقَا وَكَانَا جَمِيعًا أَوْ يُخَيِّرُ أَحَدُهُمَا الآخَرَ فَإِنْ خَيَّرَ أَحَدُهُمَا الآخَرَ فَتَبَايَعَا عَلَى ذَلِكَ فَقَدْ وَجَبَ الْبَيْعُ وَإِنْ تَفَرَّقَا بَعْدَ أَنْ تَبَايَعَا وَلَمْ يَتْرُكْ وَاحِدٌ مِنْهُمَا الْبَيْعَ فَقَدْ وَجَبَ الْبَيْعُ  

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.  

قَالَ رَسُولُ اللَّهِ ﷺ 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  

There is no transaction between two persons entering a transaction until they separate, but only when there is an option to annul it.  

قَالَ رَسُولُ اللَّهِ ﷺ كُلُّ بَيِّعَيْنِ لاَ بَيْعَ بَيْنَهُمَا حَتَّى يَتَفَرَّقَا إِلاَّ بَيْعُ الْخِيَارِ