Sunan an-Nasa'i, Hadith 3781 ⓘ
'Amr bin Shu'aib narrated from his father, from his grandfather, that the Messenger of Allah said: "Whoever swears an oath, then sees something better than it, let him do that which is better."
أَخْبَرَنَا عَمْرُو بْنُ عَلِيٍّ، قَالَ حَدَّثَنَا يَحْيَى، عَنْ عُبَيْدِ اللَّهِ بْنِ الأَخْنَسِ، قَالَ حَدَّثَنَا عَمْرُو بْنُ شُعَيْبٍ، عَنْ أَبِيهِ، عَنْ جَدِّهِ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ " مَنْ حَلَفَ عَلَى يَمِينٍ فَرَأَى غَيْرَهَا خَيْرًا مِنْهَا فَلْيُكَفِّرْ عَنْ يَمِينِهِ وَلْيَأْتِ الَّذِي هُوَ خَيْرٌ " .
also referenced under: Book 35, Hadith 21 (In-Book) & Volume 4, Book 35, Hadith 3812 (DarusSalam)