Caution: Translations of Quran and Ḥadīth may lead to possible misapplications and misinterpretations. This site is intended for students of sacred knowledge that are proficient in comprehending classical Arabic and have a strong foundation in Islamic sciences. Also note that religious injunctions rely on several aspects beyond what one may glean through reading individual aḥādīth.
Qurʾān Bukhārī Muslim Nasāʾī Abū Dāwūd Tirmidhī Ibn Mājah Mālik Aḥmad Dārimī Ḥākim Ibn Ḥibbān Ṭabarānī Nasāʾī's Kubrá Bayhaqī al-Luʾluʾ wa-al-Marjān Ibn Rajab's Fifty Riyāḍ al-Ṣāliḥīn Aḥmad's Zuhd Suyūṭī
ibnmajah:2127 – ʿAlī b. Muḥammad > Wakīʿ > Ismāʿīl b. Rāfiʿ > Khālid b. Yazīd > ʿUqbah b. ʿĀmir al-Juhanī

"Whoever makes a vow and does not state it specifically, the expiation (for such a vow) is the expiation for breaking an oath. "  

ابن ماجة:٢١٢٧ – حَدَّثَنَا عَلِيُّ بْنُ مُحَمَّدٍ حَدَّثَنَا وَكِيعٌ حَدَّثَنَا إِسْمَاعِيلُ بْنُ رَافِعٍ عَنْ خَالِدِ بْنِ يَزِيدَ عَنْ عُقْبَةَ بْنِ عَامِرٍ الْجُهَنِيِّ قَالَ

قَالَ رَسُولُ اللَّهِ ﷺ مَنْ نَذَرَ نَذْرًا وَلَمْ يُسَمِّهِ فَكَفَّارَتُهُ كَفَّارَةُ يَمِينٍ  

See similar narrations below:

Collected by Aḥmad, Suyūṭī
ahmad:17423 – Isḥāq b. ʿĪsá > Ibn Lahīʿah > Kaʿb b. ʿAlqamah > ʿAbd al-Raḥman b. Shimāsah > Abū al-Khayr > ʿUqbah b. ʿĀmir

The Messenger of Allah said: "There is no vow at a moment of anger and its expiation is the expiation for an oath." (Using translation from Nasāʾī 3843)   

أحمد:١٧٤٢٣ – حَدَّثَنَا إِسْحَاقُ بْنُ عِيسَى حَدَّثَنَا ابْنُ لَهِيعَةَ حَدَّثَنَا كَعْبُ بْنُ عَلْقَمَةَ عَنْ عَبْدِ الرَّحْمَنِ بْنِ شِمَاسَةَ عَنْ أَبِي الْخَيْرِ عَنْ عُقْبَةَ بْنِ عَامِرٍ قَالَ

قَالَ رَسُولُ اللهِ ﷺ إِنَّمَا النَّذْرُ كَفَّارَتُهُ كَفَّارَةُ الْيَمِينِ