Sunan an-Nasa'i, Hadith 3791 ⓘ
'Abdur-Rahman bin Samurah said: "The Messenger of Allah said to me: 'If you swear an oath, then you see something that is better, do that which is better, and offer expiation for your oath.'"
أَخْبَرَنَا مُحَمَّدُ بْنُ قُدَامَةَ، فِي حَدِيثِهِ عَنْ جَرِيرٍ، عَنْ مَنْصُورٍ، عَنِ الْحَسَنِ الْبَصْرِيِّ، قَالَ عَبْدُ الرَّحْمَنِ بْنُ سَمُرَةَ قَالَ لِي رَسُولُ اللَّهِ صلى الله عليه وسلم " إِذَا حَلَفْتَ عَلَى يَمِينٍ فَرَأَيْتَ غَيْرَهَا خَيْرًا مِنْهَا فَأْتِ الَّذِي هُوَ خَيْرٌ وَكَفِّرْ عَنْ يَمِينِكَ " .
also referenced under: Book 35, Hadith 31 (In-Book) & Volume 4, Book 35, Hadith 3822 (DarusSalam)