Muslim

Hadith Commentary: Benefits and Issues: From this hadith, it is understood that the ruling of a vow (nadhar) is like that of an oath (qasam), therefore its expiation (kaffarah) is also like that of an oath. In Jami' al-Saghir, it is stated:
(al-nadhru yameen)
A vow is an oath,
(wa kaffaratuhu kaffarat al-yameen)
and its expiation is the expiation of an oath.
In some narrations, it is stated:
(kaffarat al-nadhr idha lam yusamm kaffarat al-yameen)
If the vow is not specified, its expiation is the expiation of an oath.
Therefore, the meaning of this hadith will be that if someone says,
"Lillahi 'alayya nadhr,"
A vow is due from me to Allah,
then the expiation of an oath becomes obligatory upon him.
And according to Imam Nawawi, what is meant here is a vow of obstinacy (nadhr lajaaj),
in which there is a condition attached,
for example, a person says,
"If I speak to Zayd, then a pilgrimage (hajj) is due from me for Allah,"
so according to the Shafi'is, if he speaks to Zayd and thus breaks his oath,
meaning he breaks the oath,
because this vow
is of the nature of an oath,
then now he has the choice: either he fulfills the vow by performing the pilgrimage, or he pays the expiation of an oath.
This is also the position of the Hanafis.
If the vow is of disobedience (ma'siyah),
then the statements of the Imams regarding this have already been mentioned.
If a vow is made regarding something that is beyond his capacity or power,
then the expiation of an oath is due upon him.
But if he vows to go to the House of Allah (Bayt Allah) on foot,
or vows to sacrifice his son,
then according to most of the Imams, a compensatory sacrifice (dam) will be obligatory upon him.
From Ibn Abbas radi Allahu anhuma, in Sunan Abi Dawud, a marfu' hadith is narrated that whoever makes an unspecified vow,
the expiation of an oath is due upon him,
and whoever makes a vow of disobedience,
the expiation of an oath is also due upon him,
and whoever makes a vow beyond his capacity,
its expiation is also that of an oath.
And in Sunan Ibn Majah, it is stated:
Whoever makes a vow according to his ability and capacity,
he should fulfill it.
(Takmilah,
vol. 2,
p. 174)

Explanation:
1:
That is, whoever made a vow (nadhar) and did not specify it by name, meaning he only said that if his wish is fulfilled, a vow is due upon him, then its expiation (kaffarah) is the same as the expiation for an oath (yamin).

Note:
(However, the phrase 'lam yusamm' is not authentic, and apart from the author, it is not found with anyone else (whereas Abu Dawood, taking this into consideration, has titled a chapter “Whoever makes a vow and does not specify it”). This is an addition from the author’s narrator “Muhammad Mawla al-Mughira,” who himself is an unknown (majhool) narrator; he is not present in the chains of others.)

The expiation (kaffarah) for an oath is explicitly mentioned in the Noble Qur’an, and it is: feeding ten needy people, or clothing them, or freeing a slave. If one is unable to do any of these three, then he must fast for three days. And this is also the expiation for a vow (nadhar). In expiation, sequence is not necessary; rather, whichever act is easier may be performed. If the vow is for a righteous deed and one has the ability to fulfill it, then the vow itself must be fulfilled. Expiation is only in the case when fulfilling the vow is not possible, or if the vow is for a sinful act.