Is niqab/burqa/abaya a must for women? How much of that clothing comes from tradition, and how much of it comes from the religion? What does islam say about women's clothing?
The story of how the abaya came to Islam is that one of the sahaba suggested that it would be more appropriate if women wore the traditional clothing of their time. Allah then decreed it so in the Quran. We can conclude that the religious clothing was already there before it was required for women to wear - the clothing did come from tradition. However, tradition does mostly consist of religon and was probably worn much before Arabs as many paintings of Mary suggest. If we were to analyze where exactly the clothing came from we would might as well trace back to Adam and Eve. The covering of a women is required in Islam, although the specific clothes are not mentioned.
And tell the believing women to lower their gaze and guard their private parts from sin and not show of their adornment except only that which is apparent, and draw their headcovers 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 (i.e., their sisters in Islam), or their female slaves whom their right hands possess, or old male servants free of physical desires, or small children who have no sense of women's nakedness. And let them not stamp their feet so as to reveal what they hide of their adornment. And turn unto Allah altogether, O you Believers, in order that you may attain success.[An-Nur, 24:31]
Allah does not command a specific type of clothing but it says to hide your adornments and this is the reason why there are so many different types of Islamic clothing and it is not limited to the abaya.
Abu Dawood narrates:
`Aishah (RAA) said: "Asmaa' the daughter of Abu Bakr (RAA) came to see the Messenger of Allah (SAAWS) wearing a thin dress; so Allah's Messenger (SAAWS) turned away from her and said: O Asmaa', once a woman reaches the age of menstruation, no part of her body should be seen but this-and he pointed to his face and hands.
This hadith gives evidence that only the hands and face of women should show and everything else is considered their "adornments."
The reason for people wearing abaya the most is because it is considered the best way to cover their body part. Covering isn't simply placing cloth over their body it has to be loose clothing.
Abu Hurairah radiyallahu anhu reported Allah’s messenger sallallahu alaihe wasallam having said this,
"Their are two groups of people destined for the fire of hell. First, those officials who would carry with them whips looking like the tails of cows and they would use them for whipping people. Secondly, those women who would be naked despite being apparently clothed. They themselves will be inclined towards men and lure them as well. Their heads will be tall like the humps of Bukhti camels, bent onto one side (their hair will be styled in a bun). They will neither enter Paradise nor would they even smell the fragrance of Paradise which can be detected from great distances."
From this hadith we can assume that we cannot wear tight clothing that cover us- they should be loose. We shouldn't wear jeans in public or tight shirts. An abaya would be better. Also the new style of placing cloth on you head to make it look like you have more hair is haram - it just lures men which is what the hijab is suppose to be preventing.
Hadith and Quran have covered the means of women covering which does make it a must in Islam.
The answer is in Surah Noor (emphasis mine):
O Prophet, tell your wives and your daughters and the women of the believers to bring down over themselves [part] of their outer garments. That is more suitable that they will be known and not be abused. And ever is Allah Forgiving and Merciful. Surah Noor, verse 59.
This is a clear indication about wearing the jilbaab, or loose outer covering that goes over your normal clothes. (That's what jilbab means in Arabic.)
Asma, daughter of Abu Bakr, entered upon the Apostle of Allah wearing thin clothes. The Apostle of Allah turned his attention from her. He said: "O Asma, when a woman reaches the age of menstruation, it does not suit her that she displays her parts of body except this and this," and he pointed to her face and hands. Collected in Abu Dawud.
Covering the face and body is, therefore, a well-known obligation in Islam. As long as your clothes are loose and modest, you're good. As to the face, the scholars differed over it being obligatory or extra/recommended.
Also, culture plays a small part in it. For example, in Saudi Arabia, all the jilbabs are black; in Africa, it's not the same by far.
A woman must ensure that her clothing does not resemble that of men and vice-versa nor should the clothing resemble the peculiar dress of the disbelievers.
Allah Taa'la mention in the Qur'an:
O Prophet ()! Tell thy wives and thy daughters and the women of the believers to draw over them their cloaks (veils). That in the least so that they be recognised and not be . (Surah Ahzaab, Verse 59)
And remain within you homes and do not make an exhibition (of yourselves) like the displays (of the immoral women) of former times of ignorance. (Surah Ahzaab)
Rasullullah has given a warning against wearing transparent clothing which makes the body visible or light clothing which emphasizes or highlights the figure of the body. He said,
Many women are clothed but naked in reality. Such women will never enter paradise nor will they smell its fragrance.
Even transparent and netted scarves are worn to deliberately display hair and parts of the body. Women who wear transparent or tight-fitting clothing should reflect over Rasullullah's remark that such women are infact naked!. How shameful indeed to remain naked in this world and as a consequence, they won't even smell the fragrance of paradise.
Also in the Hadees Sharif it is stated that the Women not necessarily wear something covering the face but a scarf covering the head is compulsary.
In a nutshell
The most important points in the Hadith of Rasullullah regarding dressing are:
1) Our dress must cover our body adequately. Again we cannot determine what is adequate coverage on our own, as any witness to the misery of those who have tried it can readily ascertain. Shar'iah, as always, takes us out of this misery by defining it for us. For men, it is the middle part of the body from navel to knee. For women, it is the entire body except hands and face. These parts must never be exposed to any other person (except in case of genuine need e.g. medical treatment). In addition, the cloth must be neither see-through nor tight fitting.
2) Our dress should provide adornment. It should provide for decent appearance. Our appearance should not be an eyesore for decent human beings. For men, this extends the coverage requirements to include most of the body. For women, the essential requirement is that their dress should identify them as respectable ladies who would be honored not harassed. Additionally, hijab rules aim at protecting them from the gaze of other men.
3) Our dress must cover our body adequately. Again we cannot determine what is adequate coverage on our own, as any witness to the misery of those who have tried it can readily ascertain. Shar'iah, as always, takes us out of this misery by defining it for us. For men, it is the middle part of the body from navel to knee. For women, it is the entire body except hands and face. These parts must never be exposed to any other person (except in case of genuine need e.g. medical treatment). In addition, the cloth must be neither see-through nor tight fitting.
4) Nor should they be so ugly and clumsy that instead of enhancing beauty, they mar the wearer's appearance.
5) The design of our dress must avoid three deadly sins: show off, arrogance, and self indulgence. These are very serious diseases of the heart in their own right that we must avoid at all times. Our garments provide an easy opportunity to nurture them. Hence the need to be extra cautious. One Hadith states "Eat what you feel like and wear what you feel like. But avoid two things: extravagance and arrogance." [Bukhari]. At the risk of stating the obvious one should be reminded that this Hadith establishes an overriding concern that limits our choices within the realm of what is considered halal. It does not do away with the distinction between halal and haram.