Ruling on whistling for women

Firstly: 

Before looking at minor issues such as these, it should first be understood
that the basic principle with regard to acts of worship is that they are not
allowed; Allah may only be worshipped in the ways that He has prescribed in
His Book or on the lips of His Prophet (blessings and peace of Allah be upon
him). 

The basic principle concerning customs or traditions is that they are
permissible; it is not prohibited to do things that people are accustomed to
doing of ordinary things, except on the basis of evidence from sharee‘ah
which forbids that. So long as we do not find any such evidence, it is not
prohibited to do that thing. 

Shaykh al-Islam Ibn Taymiyah (may Allah have mercy on him) said: 

The basic principle with regard to customs and traditions is that they are
permissible, and none of them are to be prohibited except that which Allah
has forbidden, otherwise we will become like those referred to in the verse
in which Allah says (interpretation of the meaning): “Say (O Muhammad SAW
to these polytheists): ‘Tell me, what provision Allah has sent down to you!
And you have made of it lawful and unlawful.’ Say (O Muhammad SAW): ‘Has
Allah permitted you (to do so), or do you invent a lie against Allah?’” [Yoonus
10:59]. Hence Allah condemned the mushrikeen who ordained as religious
practices things for which Allah had not given permission, and they
prohibited things that He had not prohibited.

End quote from Majmoo‘ al-Fataawa (29/17) 

Shaykh Ibn ‘Uthaymeen (may Allah have mercy on him) said: 

The difference between customs and acts of worship: 

Worship is that which Allah and His Messenger have enjoined as a means of
drawing closer to Allah and seeking His reward. 

Custom is that which people are accustomed to with regard to food, drink,
accommodation, clothing, means of transportation, transactions and so on. 

There is another difference, which is that the basic principle concerning
acts of worship is that they are not allowed and are prohibited unless there
is evidence to prove that they are (acceptable) acts of worship, because
Allah, may He be exalted, says (interpretation of the meaning): “Or have
they partners with Allah (false gods), who have instituted for them a
religion which Allah has not allowed” [ash-Shoora 42:21]. As for
customs, the basic principle is that they are permissible, unless there is
evidence to prove that they are not allowed. Based on that, if the people
are accustomed to something and anyone tells them that it is haram, then he
is required to produce evidence; it should be said to him: Where is the
evidence that it is haram? But in the case of acts of worship, if someone
tells a person that a particular act of worship is an innovation, and he
says that it is not an innovation, we say to him: Where is the evidence that
is it is not an innovation? Because the basic principle with regard to acts
of worship is that they are not allowed unless there is evidence to prove
that they are Islamically prescribed.

End quote from Liqa’ al-Baab al-Maftooh (72/2) 

Secondly: 

In the answer to question no. 115403 we discussed
the issue of whistling and noted that the scholars differed concerning the
ruling on it, but the view that is more likely to be correct is that it is
makrooh (disliked) in the case of men. 

But in the case of women, it is even more makrooh, and it may be said that
it is haram, because it is an action that is not appropriate for women and
it is an imitation of men, and indeed of the foolish ones among men, and it
is not appropriate for a Muslim woman to do this thing under any
circumstances. So the Muslim woman is emphatically disallowed to do this
action, especially if that is in a gathering, even if only women are
present. If men are present in the gathering, then it is quite obvious that
this comes under the heading of obscenity. 

Thirdly: 

The idea that sitting with the legs crossed is a sign of gharoor (arrogance)
is a notion for which there is no evidence. The basic principle concerning
traditions and customs is that they are permissible, and this manner of
sitting comes under the heading of customs for which no prohibition has been
narrated, so it remains as is (i.e., permissible). 

Al-Bukhaari (6287) and Muslim (2100) narrated from ‘Abbaad ibn Tameem that
his paternal uncle said: I saw the Messenger of Allah (blessings and peace
of Allah be upon him) lying on his back in the mosque, putting one leg on
top of the other. 

In al-Musannaf, Ibn Abi Shaybah narrated a number of reports from the
Sahaabah and Taabi‘een, stating that they used to lie on their backs and
sit, putting one leg on top of the other, including ‘Umar ibn al-Khattaab,
his son ‘Abdullah, Ibn Mas‘ood, Bilaal, Usaamah ibn Zayd, ‘Ikrimah and
others. 

See: al-Musannaf (5/227-228) 

He narrated with a saheeh isnaad (5/228) from al-Hakam that he said: I asked
Abu Mijlaz about a man sitting and putting one leg on top of the other. He
said: There is nothing wrong with it; rather it is something that the Jews
disliked. They said that Allah created the heavens and the earth in six
days, then on the Sabbath He rose over the Throne and sat in this manner. 

However we must also pay attention to people’s traditions and customs with
regard to such matters, which vary from one time and place to another, and
one should avoid doing anything that will cause people to think badly or
speak badly of him, as much as possible. 

It says in Mataalib Ooli an-Nuha (1/351) by ar-Ruhaybaani (may Allah
have mercy on him): 

Ibn ‘Aqeel said: It is not appropriate to go against people’s customs and
traditions, out of consideration towards them and so as to avoid causing
offence, except with regard to things that are haraam, if it is customary
among them to do such things or not to care about them. In that case it is
obligatory to go against them, whether they approve of that or not. End
quote. 

Ad-Dardeer al-Maaliki (may Allah have mercy on him) said in ash-Sharh as-Sagheer
(p. 284): 

Dignity means striving to attain a level of perfection by guarding against
anything that will incur criticism on the basis of what is customary, even
if it appears to be permissible.

End quote. 

Ibn ‘Uthaymeen (may Allah have mercy on him) said: 

The guideline with regard to dignity is that one should not do or say
anything for which people will criticise him.

End quote from ash-Sharh al-Mumti‘ (11/108) 

For more information, please see also the answer to question no.
129182 

Fourthly: 

The idea that moving the feet or legs whilst sitting is not good because it
will take away barakah (blessing) from the house is also a notion for which
there is no evidence. The basic principle concerning that is that it is
permissible, as discussed in detail above. 

Whoever says that barakah will be taken away from the house because of this
action is inventing an idea for which there is no evidence in the texts and
is saying something for which there is no proof. 

Fifthly: 

With regard to women, a woman should sit in a modest and composed manner,
and she should not sit in a manner for which she will be criticised,
especially in the presence of men, even if it is basically permissible.
Modesty in all things is a sign of dignity. 

And Allah knows best.