Sahih Muslim
Book 27: The Book of Oaths
كتاب الأيمان
88 hadith in this book
Hammam b. Munabbih reported: This is what Abu Huraira reported to us from Allah's Messenger (ﷺ), and he narrated a hadith and (one) of them is that Allah's Messenger (ﷺ) said: I swear by Allah, it is more sinful in Allah's sight for one of you to persist in an oath regarding his family than payment of its expiation which Allah has imposed upon him (for breaking the oath).
حَدَّثَنَا مُحَمَّدُ بْنُ رَافِعٍ، حَدَّثَنَا عَبْدُ الرَّزَّاقِ، حَدَّثَنَا مَعْمَرٌ، عَنْ هَمَّامِ بْنِ مُنَبِّهٍ، قَالَ هَذَا مَا حَدَّثَنَا أَبُو هُرَيْرَةَ، عَنْ رَسُولِ اللَّهِ صلى الله عليه وسلم فَذَكَرَ أَحَادِيثَ مِنْهَا وَقَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " وَاللَّهِ لأَنْ يَلَجَّ أَحَدُكُمْ بِيَمِينِهِ فِي أَهْلِهِ آثَمُ لَهُ عِنْدَ اللَّهِ مِنْ أَنْ يُعْطِيَ كَفَّارَتَهُ الَّتِي فَرَضَ اللَّهُ " .
Hadith text, translations and grading are courtesy of Sunnah.com.