It is recommended for the one who swears an oath then sees that something else is better than it; To do that which is better and offer expiation for his oath
وَحَدَّثَنَا إِسْحَاقُ بْنُ إِبْرَاهِيمَ، أَخْبَرَنَا جَرِيرٌ، عَنْ سُلَيْمَانَ التَّيْمِيِّ، عَنْ ضُرَيْبِ بْنِ، نُقَيْرٍ الْقَيْسِيِّ عَنْ زَهْدَمٍ، عَنْ أَبِي مُوسَى الأَشْعَرِيِّ، قَالَ أَتَيْنَا رَسُولَ اللَّهِ صلى الله عليه وسلم نَسْتَحْمِلُهُ فَقَالَ " مَا عِنْدِي مَا أَحْمِلُكُمْ وَاللَّهِ مَا أَحْمِلُكُمْ " . ثُمَّ بَعَثَ إِلَيْنَا رَسُولُ اللَّهِ صلى الله عليه وسلم بِثَلاَثَةِ ذَوْدٍ بُقْعِ الذُّرَى فَقُلْنَا إِنَّا أَتَيْنَا رَسُولَ اللَّهِ صلى الله عليه وسلم نَسْتَحْمِلُهُ فَحَلَفَ أَنْ لاَ يَحْمِلَنَا فَأَتَيْنَاهُ فَأَخْبَرْنَاهُ فَقَالَ " إِنِّي لاَ أَحْلِفُ عَلَى يَمِينٍ أَرَى غَيْرَهَا خَيْرًا مِنْهَا إِلاَّ أَتَيْتُ الَّذِي هُوَ خَيْرٌ " .
Abu Musa al-Ash'ari reported: We came to Allah's Messenger (ﷺ) requesting him to provide us with riding camels. He (the Holy Prophet) said: There is nothing with me with which I should equip you. By Allah, I would not provide you with (riding camels). Then Allah's Messenger (ﷺ) sent to us three camels with spotted bumps. We said: We came to Allah's Messenger (ﷺ) asking him to equip us with riding animals. He took an oath that he could not equip us. We came to him and informed him. He said: By Allah, I do not take an oath, but when I find the other thing better than that, I do that which is better.