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." (JA)
English reference (JA): Vol. 3, Book 11, Hadith 2128 (JA)
Arabic reference (JA): Book 11, Hadith 2209 (JA)