I went along with some men from the Ash-ariyin to Messenger of Allah ﷺ and it happened that I met him while he was in an angry mood. We asked him to provide us with mounts, but he swore that he would not give us any. Later on he said, "By Allah, Allah willing, if ever I take an oath (to do something) and later on I find something else better than the first, then I do the better one and give expiation for the dissolution of my oath."  

أَتَيْتُ رَسُولَ اللَّهِ ﷺ فِي نَفَرٍ مِنَ الأَشْعَرِيِّينَ فَوَافَقْتُهُ وَهْوَ غَضْبَانُ فَاسْتَحْمَلْنَاهُ فَحَلَفَ أَنْ لاَ يَحْمِلَنَا ثُمَّ قَالَ وَاللَّهِ إِنْ شَاءَ اللَّهُ لاَ أَحْلِفُ عَلَى يَمِينٍ فَأَرَى غَيْرَهَا خَيْرًا مِنْهَا إِلاَّ أَتَيْتُ الَّذِي هُوَ خَيْرٌ وَتَحَلَّلْتُهَا  

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  

"مَا أنَا حَمَلتُكُمْ (*) وَلَكِنَّ الله حَمَلَكُمْ، وَإِنّى وَالله -إِن شَاءَ الله- لَا أَحْلِفُ عَلَى يَمِينٍ فَأرَى غَيرَهَا خَيرًا مِنْهَا إِلَّا كَفَّرْتُ عَنْ يَمِينِى، وَأتَيتُ الذِى هُوَ خيرٌ".  

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