lt was narrated from Ibn ‘Abbas that the Prophet (peace be upon him) 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 fulfil it, the expiation for that is the expiation for breaking an oath. Whoever makes a vow and is able to fulfil it, let him do so.”
Sunan Ibn Majah, Vol. 3, Book 11, Hadith 2209