Trust (amaanah) in Islam, Dought & clear, - * Ruling on avoiding eating meat during the first ten days of Muharram

My husband's family customarily avoid eating meat from the beginning
of Muharram until the tenth of the month, and they say that this was a
covenant that their forefathers took upon themselves, therefore each
one of them must adhere to this covenant. Is this permissible?
Praise be to Allah
Refraining from eating permissible things that Allah has allowed comes
under the heading of monasticism that was prohibited by Allah, may He
be exalted, and His Messenger. Shaykh al-Islam Ibn Taymiyah (may Allah
have mercy on him) said:
Monasticism means giving up things that are permissible, such as
marriage, eating meat, and so on. A group among the Sahaabah (may
Allah be pleased with them) thought of following some monastic
practices, but Allah, may He be exalted, sent down revelation
forbidding them to do that, as He said (interpretation of the
meaning):"O you who believe! Make not unlawful the Taiyibat (all that
is good as regards foods, things, deeds, beliefs, persons, etc.) which
Allah has made lawful to you, and transgress not. Verily, Allah does
not like the transgressors" [al-Maa'idah 5:87]. And it is proven
inas-Saheehaynthat there was a group of the Companions of the Prophet
(blessings and peace of Allah be upon him), one of whom said: As for
me, I will fast and never not fast. Another said: As for me, I will
pray qiyaam (voluntary prayers at night) and never sleep. Another
said: As for me, I will not marry women. Another said: As for me, I
will not eat meat. The Prophet (blessings and peace of Allah be upon
him) stood up to deliver a speech and said: What is the matter with
men of whom one says such and such? But I fast and do not fast, I pray
qiyaam and I sleep, I marry women, and I eat meat. Whoever turns away
from my Sunnah is not of me." The saheeh texts explain that
monasticism is an innovation and misguidance.
End quote fromal-Jawaab as-Saheeh(2/194-197)
To sum up: whoever seeks to worship Allah, may He be exalted, by
refraining from eating meat or from other permissible things on
specific days, this comes under the heading of prescribing religious
practice for which Allah has not given permission.
That applies whether this is due to a belief that these days have some
special characteristic that dictates refraining from eating meat,
or because one regards it as haraam or makrooh
or because of a belief that refraining from eating meat during these
days is obligatory or mustahabb
or because of a belief that one may draw closer to Allah by refraining
from eating meat or from other permissible things in a particular way.
All of that comes under the heading of innovations and misguidance for
which Allah has not given permission.
Ash-Shaatibi (may Allah have mercy on him) said:
Everyone who restricts himself from consuming that which Allah has
permitted, without a legitimate shar'i reason for doing so, has
diverged from the Sunnah of the Prophet (blessings and peace of Allah
be upon him), and the one who acts upon something other than the
Sunnah by way of a religious practice is essentially an innovator.
End quote fromal-I'tisaam(p. 59)
Shaykh al-Islam Ibn Taymiyah (may Allah have mercy on him) said:
Allah, may He be exalted, commanded mankind to worship Him alone and
not to associate anything with Him in worship, and to worship Him
according to what He prescribed; and He commanded that they should not
worship Him by any acts of worship other than that. Allah, may He be
exalted, says (interpretation of the meaning):
"So whoever hopes for the Meeting with his Lord, let him work
righteousness and associate none as a partner in the worship of his
Lord"
[al-Kahf 18:110]
"…that He might try you, which of you is the best in deeds"
[Hood 11:7].
With regard to the one who follows the path of asceticism and worship,
if he appears outwardly to be following Islamic teachings, but his
intention is to show off, gain a good reputation and gain people's
respect, then his good deeds are invalid and are not acceptable to
Allah. It is proven inas-Saheehthat Allah says: "I am the least in
need of a partner. Whoever does any deed in which he associates
someone else with Me, I disavow him and all of his deeds are for the
one whom he associated with Me." And in as-Saheeh it is narrated that
the Prophet (blessings and peace of Allah be upon him) said: "Whoever
talks about his good deeds (to show off), Allah will expose him (on
the Day of Resurrection), and whoever makes a (hypocritical) display,
Allah will make a display of him."
If he is sincere in his intention, but he worships Allah by doing acts
of worship other than those that are prescribed, such as one who
remains silent constantly, or stands in the sun or on the roof
constantly, or does not wear ordinary clothes, and always wears wool
or sackcloth, and the like, or covers his face, or refrains from
eating bread or milk, or drinking water, and so on – these acts of
worship are invalid and are to be rejected, as it is proven
inas-Saheehin a report from 'Aa'ishah that the Prophet (blessings and
peace of Allah be upon him) said: "Whoever introduces anything into
this matter of ours that is not part of it will have it rejected.
And it is proven from him inas-Saheehthat there was a group among his
Companions, one of whom said: As for me, I will fast and never not
fast. Another said: As for me, I will pray qiyaam (voluntary prayers
at night) and never sleep. Another said: As for me, I will not marry
women. Another said: As for me, I will not eat meat. The Prophet
(blessings and peace of Allah be upon him) stood up to deliver a
speech and said: What is the matter with men of whom one says such and
such? But I fast and do not fast, I pray qiyaam and I sleep, I marry
women and I eat meat. Whoever turns away from my Sunnah is not of me."
So this is the principle with regard to acts of worship, because
fasting and prayer are both acts of worship.
Refraining from eating meat or getting married is permissible in
principle, but when that went beyond the framework of the Sunnah and
the individual committed himself to more than is prescribed, or
committed himself to refraining from that which is permissible, as
monks do, the Prophet (blessings and peace of Allah be upon him)
disavowed those who do such things as having turned away from his
Sunnah towards something else, and he said: "There is no monasticism
in Islam."
End quote fromMajmoo' al-Fataawa(11/612-614)
Conclusion:
Having the custom of not eating meat during these days, in the manner
mentioned – whether that was based on a covenant with Allah, or with
other people, or with one's own self, or without any covenant – all
comes under the heading of innovation that is not permissible as a
means of drawing closer to Allah, may He be exalted, and it is not
permissible to obey one's parents and grandparents concerning that, or
to follow them in doing it.
And Allah knows best.