The Book of Oaths
وَحَدَّثَنِي أَبُو الطَّاهِرِ، حَدَّثَنَا عَبْدُ اللَّهِ بْنُ وَهْبٍ، أَخْبَرَنِي مَالِكٌ، عَنْ سُهَيْلِ بْنِ أَبِي، صَالِحٍ عَنْ أَبِيهِ، عَنْ أَبِي هُرَيْرَةَ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ " مَنْ حَلَفَ عَلَى يَمِينٍ فَرَأَى غَيْرَهَا خَيْرًا مِنْهَا فَلْيُكَفِّرْ عَنْ يَمِينِهِ وَلْيَفْعَلْ " .Abu Huraira reported Allah's Messenger (ﷺ) as saying:He who took an oath and then found another thing better than (this) should expiate for the oath (broken) by him and do (the better thing)
From Sahih Muslim, whose reports the scholars accept as authentic.