So, what do the Quran and Sunna say about hijab? There are two ayat of the Quran that deal with hijab. These are Surah an-Nur ayah 31 and Surah al-Ahzab ayah 59. Let's look at what these ayat say, and how the Prophet (sAas) has explained them.
Surah an-Nur ayah 31 says:
Wa qul li al-mu'minat yaghdudna min absarihinna wa yahfazna furujahunna wa laa yubdina zenatahunna illa maa zahara min haa wal-yadribna bi khumurihinna ala juyubihinna; wa laa yubdina zenatahunna illa li bu'ulatihinna aw aba'ihinna aw aba'i bu'ulatihinna aw abna'ihinna aw abna'i bu'ulatihinna aw ikhwanihinna aw bani ikhwanihinna aw bani akhawatihinna aw nisa'ihinna aw maa malakat aymanu hunna aw at-tabi'ina ghayri ulu'l-irbat min ar-rijal aw at-tifl alladhina lam yazharu ala awrat an-nisa wa laa yadribna bi arjulihinna li yu'lama maa yukhfina min zenatahinna. Wa tubu ilaAllahi jami'an, ayyuha al-mu'minun la'allakum tuflihun
And say to the faithful women to lower their gazes, and to guard their private parts, and not to display their beauty except what is apparent of it, and to extend their headcoverings (khimars) to cover their bosoms (jaybs), and not to display their beauty except to their husbands, or their fathers, or their husband's fathers, or their sons, or their husband's sons, or their brothers, or their brothers' sons, or their sisters' sons, or their womenfolk, or what their right hands rule (slaves), or the followers from the men who do not feel sexual desire, or the small children to whom the nakedness of women is not apparent, and not to strike their feet (on the ground) so as to make known what they hide of their adornments. And turn in repentance to Allah together, O you the faithful, in order that you are successful
Surah al-Ahzab ayah 59 says:
Ya ayyuha an-Nabiyy qul li azwajika wa banatika wa nisa al-mu'minin yudnina alayhinna min jalabib hinna; dhalika adna an yu'rafna fa laa yu'dhayn. Wa kana Allahu Ghafur Rahim
O Prophet! Say to your wives and your daughters and the women of the faithful to draw their outergarments (jilbabs) close around themselves; that is better that they will be recognized and not annoyed. And God is ever Forgiving, Gentle.
Together, these two ayat lay out seven commandments for Muslim sisters:
"to lower their gazes"
"to guard their private parts"
"not to display their beauty except what is apparent of it"
"to extend their headcoverings to cover their bosoms"
"not to display their beauty except to their husbands or their fathers..."
"not to strike their feet (on the ground) so as to make known what they hide"
"to draw their outergarments close around themselves"
It can be seen that three of these commandments relate to behavior. These are:
lowering the gaze
guarding the private parts
not striking the feet on the ground so as to give knowledge of what is hidden
Lowering the gaze means not looking at what is forbidden to be seen of others. Guarding the private parts means that only the husband is allowed to see or touch them. Not giving knowledge of what is hidden means not posturing or strutting around so as to jangle hidden jewelry or make men think about hidden body parts. All of these are part of what Allah SWT has commanded in regard to hijab.
The other four commandments relate to dress, and can really be expressed as three rules:
not displaying the beauty beyond "what is apparent of it" except to the people listed in 24:31
extending the headcovering to cover the bosom
drawing the outergarment close around
http://www.muhajabah.com/whyhijab.htm