صَحِيحُ مُسْلِمٍ
Sahih Muslim 1651 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
وَحَدَّثَنَا عُبَيْدُ اللَّهِ بْنُ مُعَاذٍ، حَدَّثَنَا أَبِي، حَدَّثَنَا شُعْبَةُ، عَنْ عَبْدِ الْعَزِيزِ بْنِ رُفَيْعٍ، عَنْ تَمِيمِ بْنِ طَرَفَةَ، عَنْ عَدِيِّ بْنِ حَاتِمٍ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم مَنْ حَلَفَ عَلَى يَمِينٍ فَرَأَى غَيْرَهَا خَيْرًا مِنْهَا فَلْيَأْتِ الَّذِي هُوَ خَيْرٌ وَلْيَتْرُكْ يَمِينَهُ .
'Adi b. Hatim reported Allah's Messenger (ﷺ) as saying: He who took an oath, but he found something else better than that, should do that which is better and break his oath.
Sahih Muslim, 1651 bSahihصحيح