Sunan Ibn Majah
2127
Daif+3

It was narrated from 'Uqbah bin 'Amit Al-Juhani that the Messenger of Allah (ﷺ) said:"Whoever makes a vow and does not state it specifically, the expiation (for such a vow) is the expiation for breaking an oath

DaifAl-Albani
SahihMuhammad Fouad Abd al-Baqi