She vowed that if the arguments with her husband ceased, she would fast on Thursdays forever

Question

Praise be to Allah.

This is what
the scholars called a conditional vow (nadhr mu’allaq), as the vow is
subject to the condition that a certain thing happen. The ruling on this is
that if the thing vowed is an act of worship and the thing stated as the
condition comes to pass, it become obligatory to fulfil the vow, because the
Prophet (peace and blessings of Allaah be upon him) said: “Whoever
vows to obey Allaah then let him obey Him, and whoever vows to disobey
Allaah let him not disobey Him.” Narrated by al-Bukhaari, 6318.

Ibn Qudaamah
(may Allaah have mercy on him) said concerning vows to do acts of worship:
“These are of three types, one of which is doing the acts of worship in
return for a blessing bestowed or a harm warded off, such as if a person
says, ‘If Allaah heals me, then I will fast one month for Allaah.’ So this
act of worship becomes binding because it is obligatory in principle in
sharee’ah, like fasting, prayer, charity and Hajj, and it is obligatory to
fulfil this vow according to scholarly consensus.”

Al-Mughni,
13/622

The
condition in the case of this vow is the cessation of arguments between this
woman and her husband, without divorce.

One of the
following two scenarios must apply in this woman’s case.

Either she
wanted a specific argument that was taking place at the time of the vow to
cease without divorce, in which case she is obliged to fulfil the vow
because the condition was met, which is that the argument ceased without
divorce, and the divorce that took place after that does not matter because
that had to do with a different argument,

Or she
wanted the arguments that were taking place between her and her husband for
a particular reason to cease altogether, so that they would not happen
again. In this case she is not obliged to observe these fasts, because the
condition was not fulfilled, as the arguments happened again and divorce
occurred as a result. Perhaps what she says in her question, “but Allaah
decreed that the same argument should arise again”, is indicative of that.

This woman
should define what she meant, and then do whatever she is obliged to do
according to sharee’ah.

It should be
noted that vows are makrooh in principle, because of the report narrated by
al-Bukhaari (6608) and Muslim (1639) from Ibn ‘Umar (may Allaah be pleased
with him), that the Prophet (peace and blessings of Allaah be upon him)
forbade vows and said: “They do not change anything, they only make a stingy
person give (in charity).”

Al-Maaziri said: It may
be understood that the reason for them not being allowed is that a vow
becomes binding, and he may do it under compulsion, without enthusiasm. Or
it may be understood that the reason is that he may offer the sacrifice that
he promised in his vow in return for the things that he asked for, and thus
his reward will be reduced. The point of worship is that it should be purely
for the sake of Allaah. Al-Qaadi ‘Iyaad said: It may be understood that the
prohibition is because some ignorant people may think that the vow changes
the divine decree and prevents the divine decree from being carried out, so
it was forbidden lest some ignorant people believe that. The context of the
hadeeth supports that. And Allaah knows best.

From
Sharh Muslim by al-Nawawi.

The believer
should avoid doing that which the Prophet (peace and blessings of
Allaah be upon him) disallowed. Whoever wants to obey or worship Allaah, let him do so without making vows.

And Allaah knows best.