Allah the Exalted says in Surat an-Noor, ayah 31:
And tell the believing women to lower their gaze and guard their private parts and not show of their adornment except only that which is apparent, and draw their veils over their (necks and) bosoms and not reveal their adornment except to their husbands, their fathers, their husbands' fathers, their sons, their husbands' sons, their brothers, or their brothers' sons, or their sisters' sons, or their women, or their slaves, or male servants who lack vigor, or small children who have no knowledge of women's private parts. And let them not stamp their feet so as to reveal what they hide of their adornment. And turn you all to Allah in repentance, O believers, that you may be successful.
And He says in Surat al-Ahzab, ayah 59:
Oh Prophet, tell your wives and your daughters and the women of the believers to draw their outer garments close around them. That will be better, that they may be known and so not be bothered. And Allah is oft-forgiving, most merciful.
From these two ayat of the Noble Qur'an and from the authentic sources of guidance provided for us, we can derive the following principles of proper dress and adornment for Muslim women:
1st Requirement: The outer garment worn in public must cover all of the body except the face and hands
The first bit of guidance given in Islam describes the parts of the body which must be covered in public.
Surat an-Noor, ayah 31 (quoted above) contains a clear command that a woman's natural beauty and her adornment are to be concealed from strangers, except that which might show unintentionally (i.e. parts of the dress or ornaments) or which show as a matter of course because it is not prohibited that they be shown (i.e. the face and the hands).
Abu Dawud narrated that 'A'ishah said:
Asma came to see the Messenger of Allah (saws). She was wearing a thin dress; the Prophet (saws) turned away from her and said to her: "O Asma, once a woman reaches the age of puberty no part of her body should be uncovered except her face and hands."
For Women: In general, standards of modesty call for a woman to cover her body, particularly her chest. The Quran calls for women to "draw their head-coverings over their chests" (24:30-31), and the Prophet Muhammad instructed that women should cover their bodies except for their face and hands. Most Muslims interpret this to require head coverings for women, although some Muslim women, especially those of more conservative branches of Islam, cover the entire body, including the face and/or hands, with a full body chador.
For Men: The minimum amount to be covered on the body is between the navel and the knee. It should be noted, though, that a bare chest would be frowned upon in situations where it draws attention.
2nd Requirement: Looseness
Islam also guides that clothing must be loose enough so as not to outline or distinguish the shape of the body. Skin-tight, body-hugging clothes are discouraged for both men and women. When in public, some women wear a light cloak over their personal clothing as a convenient way to hide the curves of the body. In many predominantly Muslim countries, men's traditional dress is somewhat like a loose robe, covering the body from the neck to the ankles.
3rd Requirement: Thickness
The Prophet Muhammad once warned that in later generations, there would be people "who are dressed yet naked." See-through clothing is not modest, for either men or women. The clothing must be thick enough so that the color of the skin it covers is not visible, nor the shape of the body underneath.
4th Requirement: Overall Appearance
The overall appearance of a person should be dignified and modest. Shiny, flashy clothing may technically meet the above requirements for exposure of the body, but it defeats the purpose of overall modesty and is therefore discouraged.
5th Requirement: Not Imitating Other Faiths
Islam encourages people to be proud of who they are. Muslims should look like Muslims and not like mere imitations of people of other faiths around them. Women should be proud of their femininity and not dress like men. And men should be proud of their masculinity and not try to imitate women in their dress. For this reason, Muslim men are forbidden from wearing gold or silk, as these are considered feminine accessories.
6th Requirement: Decent But Not Flashy
The Quran instructs that clothing is meant to cover our private areas and be an adornment (Quran 7:26). Clothing worn by Muslims should be clean and decent, neither excessively fancy nor ragged. One should not dress in a manner intended to gain the admiration or sympathy of others.
7th Requirement: The clothes of Muslim women should not resemble men's clothes.
Abu Hurairah said that:The Messenger of Allah (saws) cursed the man who wears women's clothes and the woman who wears men's clothes.Ibn Umar said that he heard the Messenger of Allah (saws) say: He is not of us who imitates women nor is he of us who imitates men."Al Hakim
Abdullah Ibn Umar reported that the Prophet (saws) said:Three people will not enter paradise, and Allah will not look at them on the day of Judgment: the one who is disobedient to his parents, the woman who imitates men and the ad-dayooth.Ahmad
Ad-dayooth is the man who permits women for whom he is responsible to engage in illicit sexual relations, or to display their beauty to strange men, thereby stimulating their sexual desires.
8th Requirement: Muslim women are not to wear perfume in public.
Abu Musa narrated that the Prophet (saws) said:
Any woman who wears perfume and passes by some people who smell her perfume is like one who commits fornication.
Abu Hurairah said that:A woman passed by him smelling strongly of scent. He called to her: "O slave of the powerful, are you going to the mosque?" She said that she was. He said: "Go back and wash it off. I heard the Messenger of Allah (saws) say: 'Any woman who goes to the mosque wearing perfume will not have her prayer accepted by Allah; first she should go back home and have a bath [to wash it off].'"
9th Requirement: Beyond the Clothing: Behaviors and Manners
Islamic clothing is but one aspect of modesty. More importantly, one must be modest in behavior, manners, speech, and appearance in public. The dress is only one aspect of the total being and one that merely reflects what is present on the inside of a person's heart.
10th Requirement :The clothing of Muslim women should not be ostentatious.
Ibn Umar reported that the Messenger of Allah (saws) said:He who dresses for ostentation in this world, Allah will dress him in a dress of humiliation on the Day of Judgment and set it on fire.Abu Dawud
Is Islamic Clothing Restrictive?
Islamic dress sometimes draws criticism from non-Muslims; however, dress requirements are not meant to be restrictive for either men or women. Most Muslims who wear a modest dress do not find it impractical in any way, and they are able to easily continue with their activities in all levels and walks of life.
There are, however, some additional prohibitions regarding personal appearance of which our Muslim sisters should be aware. These prohibitions have to do with changes made to the appearance which are regarded as unacceptable alterations to Allah's creation, namely wearing wigs, plucking facial hair, filing teeth and getting tattoos.
Asma related that:
A woman asked the Prophet (saws):"Messenger of Allah, my daughter had smallpox, and as a result her hair fall out. She has recently been married; can I get her a wig?" He answered: " Allah has cursed the maker and wearer of a wig."
Abdullah said that Allah (swt) has cursed tattooers and those who are tattooed, and those women who have their teeth filed for beauty and those who have their hair plucked and thus alter Allah's creation.
A woman asked him: "What is all this?" He replied: "Should I not curse one whom Allah's Messenger has cursed? And it is in the Book of Allah." She said: I read the Qur'an from cover to cover but did not find that in it. "He said: If you had read it thoroughly you would have found it. Allah says "Whatever Allah's Messenger gives you, take it, and whatever he has forbidden, refrain from it Qur'an 69: 7
(Muslim)