The Messenger of Allah ﷺ said, "The expiation for breaking a vow is the same as the expiation for breaking an oath."
حدثنا هارون بن عباد الأزدي حدثنا أبو بكر يعني ابن عياش عن محمد مولى المغيرة قال حدثني كعب بن علقمة عن أبي الخير
قال رسول الله ﷺ كفارة النذر كفارة اليمين
No references are available.
Sourcing, sahih. Reported by Tirmidhi, in the chapter on vows and oaths, the section on what has come regarding the expiation for an unspecified vow, hadith 1528, from the hadith of Abu Bakr bin Ayyash, with this chain, and he said, hasan sahih gharib. Muslim also reported it, hadith 1645, through another route from Abu Khayr, with this chain.