That her father (Abu Bakr) never broke his oath till Allah revealed the order of the legal expiation for oath. Abu Bakr said, "If I ever take an oath (to do something) and later find that to do something else is better, then I accept Allah's permission and do that which is better, (and do the legal expiation for my oath ) ".  

أَنَّ أَبَاهَا كَانَ لاَ يَحْنَثُ فِي يَمِينٍ حَتَّى أَنْزَلَ اللَّهُ كَفَّارَةَ الْيَمِينِ قَالَ أَبُو بَكْرٍ لاَ أَرَى يَمِينًا أُرَى غَيْرَهَا خَيْرًا مِنْهَا إِلاَّ قَبِلْتُ رُخْصَةَ اللَّهِ وَفَعَلْتُ الَّذِي هُوَ خَيْرٌ  

On the authority of his father that the Prophet ﷺ said: I swear by Allah that if Allah wills I shall swear on an oath and then consider something else to be better than it without making atonement for my oath and doing the thing that is better. Or he said (according to another version): But doing the thing that is better and making atonement for my oath.  

أَنَّ النَّبِيَّ ﷺ قَالَ إِنِّي وَاللَّهِ إِنْ شَاءَ اللَّهُ لاَ أَحْلِفُ عَلَى يَمِينٍ فَأَرَى غَيْرَهَا خَيْرًا مِنْهَا إِلاَّ كَفَّرْتُ عَنْ يَمِينِي وَأَتَيْتُ الَّذِي هُوَ خَيْرٌ أَوْ قَالَ إِلاَّ أَتَيْتُ الَّذِي هُوَ خَيْرٌ وَكَفَّرْتُ يَمِينِي  

[Machine] The Messenger of Allah ﷺ used to never break his oath until Allah revealed the expiation for oaths. He said, "I will not swear by an oath, seeing something better than it, unless I expiate for the oath and then do what is better."  

كَانَ رَسُولُ اللَّهِ ﷺ إِذَا حَلَفَ عَلَى يَمِينٍ لَا يَحْنَثُ حَتَّى أَنْزَلَ اللَّهُ تَعَالَى كَفَّارَةَ الْيَمِينِ فَقَالَ «لَا أَحْلِفُ عَلَى يَمِينٍ فَأَرَى غَيْرَهَا خَيْرًا مِنْهَا إِلَّا كَفَّرْتُ عَنْ يَمِينٍ ثُمَّ أَتَيْتُ الَّذِي هُوَ خَيْرٌ»  

[Machine] The Prophet ﷺ, when he used to swear by an oath, he would not break it until the expiation for the oath was revealed. Then he ﷺ would say, "I do not swear by an oath and then see something better than it except that I fulfill the better one and compensate for my oath."  

كَانَ رَسُولُ اللَّهِ ﷺ إِذَا حَلَفَ عَلَى يَمِينٍ لَمْ يَحْنَثْ حَتَّى نَزَلَتْ كَفَّارَةُ الْيَمِينِ فَقَالَ ﷺ «لَا أَحْلِفُ عَلَى يَمِينٍ فَأَرَى غَيْرَهَا خَيْرًا مِنْهَا إِلَّا أَتَيْتُ الَّذِي هُوَ خَيْرٌ وَكَفَّرْتُ عَنْ يَمِينِي»  

Abu Bakr As-Siddiq had never broken his oaths till Allah revealed the expiation for the oaths. Then he said, "If I take an oath to do something and later on I find something else better than the first one, then I do what is better and make expiation for my oath." (Using translation from Bukhārī 6621)   

أَبَا بَكْرٍ ؓ لَمْ يَحْنَثْ فِي يَمِينٍ قَطُّ حَتَّى أَنْزَلَ اللهُ كَفَّارَةَ الْيَمِينِ فَقَالَ لَا أَحْلِفُ عَلَى يَمِينٍ فَرَأَيْتُ غَيْرَهَا خَيْرًا مِنْهَا إِلَّا أَتَيْتُ الَّذِي هُوَ خَيْرٌ وَكَفَّرْتُ عَنْ يَمِينِي  

"إِنِّى واللَّه إِنْ شاءَ اللَّه لا أَحْلِفُ على يمين فأَرى غيْرَها خيْرًا مِنْهَا إِلَّا كفَّرتُ عن يمينى وأَتيتُ الَّذى هُوَ خيْرٌ".  

"عَنْ عَائِشَةَ: أَنَّ أَبَا بَكْرٍ لَمْ يَكُنْ يَحْنَثُ فِي يَمِينٍ يَحْلِفُ بِهَا حَتَّى أَنْزَلَ اللهُ كَفَّارَةَ اليَمِينِ، فَقَالَ: وَاللهِ لَا أَدَعُ يَمِينًا حَلَفْتُ عَلَيْهَا أَرَى غَيْرَهَا خَيْرًا مِنْهَا إِلَّا قَبِلْتُ رُخْصَةَ اللهِ، وَفَعَلْتُ الَّذِي هُوَ خَيْر".