lt was narrated from Ibn 'Abbas that the Prophet (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. Whoever makes a vow and is not able to fulfill it, the expiation for that is the expiation for breaking an oath. Whoever makes a vow and is able to fulfill it, let him do so."
English reference: Vol. 3, Book 11, Hadith 2128
Arabic reference: Book 11, Hadith 2209