صَحِيحُ مُسْلِمٍ
Sahih Muslim 1650 b
The Book of Oaths
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
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).
Sahih Muslim, 1650 bSahihصحيح