Islam has given guidelines for women to be followed both for when she is in her house and when she leaves her house out of necessity.
The First Degree of Hijab:
The first degree of Hijab is Hijab against people in that women themselves and even what they do should not be seen by men. In normal times, they should remain in their house and the gaze of men should not fall even on their clothes. This is a high degree of Hijab. Allah (Subhanahu Wa Ta'ala) says:
And stay quietly in your houses, and make not a dazzling display, like that of the Jahili period (i.e. before the revelation of the Holy Quran); and establish regular Prayer, and give regular Charity; and obey Allah and His Messenger.
And remain in your houses with calm and peace and do not display adornment like that of the day of ignorance. Surah Ahzaab (33:33)
Allah (Subhanahu Wa Ta'ala) also says:
Translation: - And when You (Sallallahu alaihi wa sallam) ask them (the pure wives) for something, ask them from behind a curtain. Surah Ahzaab (33:53)
There is a Hadith in Jame Tirmidhi, Sunan Abu Dawood and Musnad Ahmed:
Translation of Hadith: It has been narrated on the authority of Hadhrat Umme Salma (May Allah be well pleased with her) that she and Hadhrat Maimoona (May Allah be well pleased with her) were in the presence of the Holy Prophet (Sallallahu alaihi wa sallam) and Hadhrat Abdullah bin Maktoom (May Allah be well pleased with him) entered. The Holy Prophet (Sallallahu alaihi wa sallam) said: Hijab yourselves from him. Hadhrat Umme Salma (May Allah be well pleased with him) says: I said: O Prophet of Allah! He is blind, he can’t see us. He (Sallallahu alaihi wa sallam) said: Are you also blind? Can you not see him?
(Jame Tirmidhi, Hadith No: 2702, Sunan Abu Dawood, Hadith No: 3585, Musnad Imam Ahmed, Hadith No: 2702)
The welfare of women in this world and the safety of their honor and chastity lies in the secret that neither they should see non-Mahram men nor should they reveal themselves to non‑Mahram, as related from Syeda Fatima Zahra (May Allah Ta'ala be well pleased with her)
There is a Hadith in Kanz Ul Ummal and Majma Uz Zawaaid:
Translation of Hadith: It has been narrated on the authority of Hadhrat Ali (May Allah be well pleased with him) that I was in the presence of the Holy Prophet (Sallallahu alaihi wa sallam). He told the Sahabah: What is better for a woman? The Sahabah remained silent. Then when I went to my house, I asked Hadhrat Fatima (May Allah be well pleased with her) about this. She said: It is better for women that they do not see men and men don’t see them. When I conveyed this reply to the Holy Prophet (Sallallahu alaihi wa sallam), He (Sallallahu alaihi wa sallam) said: She has said the truth. Verily! She is a piece of my heart.
(Majma Uz Zawaaid, Vol. 4, Pg No: 255, Kanz Ul Ummal, Hadith No: 46012)
The Second Degree
When women are allowed to leave the house for any valid need of theirs, then they are ordered to cover themselves in a long chador or similar type of cloth in such a way that no part of their body should be visible. She should not use any kind of scent, fragrance, etc. She should not wear any jewelry which produces any sound. She should walk by the sides of the road and she should not enter a crowd of men. As Allah (Subhanahu Wa Ta'ala) says in Surah Ahzaab:
Translation: - O Prophet (Sallallahu alaihi wa sallam)! Say to your wives, your daughters and the women of believer that (while going out) they should draw their veils (Hijab) as covering over them. It is more likely that this way they may be recognized (as pious, free women) and may not be hurt (considered by mistake as roving slave girls). And Allah is Most Forgiving, Ever Merciful. Surah Ahzaab (33:59)
The Third Degree
In the house, there is no prohibition on relatives, servants, etc. entering the house and collective living, eating etc. with them. Broad guidelines have been given in this regard.
And say to the believing women that they should lower their gaze and guard their modesty; that they should not display their beauty and ornaments except what (ordinarily) appear thereof; that they should draw their Hijabs over their bosoms and not display their beauty except to their husbands, fathers, husbands' fathers, sons, husbands' sons, brothers, or brothers' sons, or sisters' sons, or women, or the slaves whom their right hands possess or male servants free of physical needs, or small children who have no sense of sex; and that they should not strike their feet in order to draw attention to their hidden ornaments. And O ye Believers! Turn ye all together towards Allah that ye may attain Bliss.
And turn to Allah all of you in repentance, O believers, so that you may prosper (by implementing these Commandments). Surah Noor (24:31)
It is but natural that all relations are not the same. Some of those revered relations, about whom one cannot even think in a wrong/indecent manner and they themselves protect each other's chastity and honor. Some are those about whom one can think in such a manner. Consequently, Islam has maintained a difference in the rules for Mahram and non-Mahram.
“Mahram” are those with whom marriage is forever prohibited, like father, maternal and paternal grandfather, brother, maternal and paternal uncle, nephew, grandson, father-in-law, etc. There are some other relatives with whom marriage is not prohibited and it is allowed and permissible, like cousins, brother-in-law, etc. They are not included in the Mahram. The Mahram are those who safeguard the chastity of women. About others Islam has ordered Hijab against them.
In the Holy Quran the Hijab for women has been dealt with in 7 verses; 3 verses of Surah Noor and 4 verses of Surah Ahzaab. There are about 70 Hadith in which the rules of Hijab have been described.
With the husband, there is no Hijab. The husband can see the wife from head to toe and vice versa. It is mentioned in etiquettes (Aadaab in Urdu) that they should not see each other’s private parts. As given in Mausu’atul Fiqhiya, Vol. 1, Pg No: 53. About other relatives like father, brother etc., the rule is that from a woman’s navel to her knees, nobody can see her. Nobody from even among the Mahram can see this area of a woman’s body. Other parts like face, ankles, arms, etc can be seen provided there is no fear of corruption, as given in Hidayah, Kitab Ul Karahiya, Pg No: 461.
The evidence of seeing the Mahram is the Word of Allah Ta'ala is in verse 31 of Surah Noor.
It is allowed to reveal one's beauty before the relations mentioned in the above verse. Revealing one’s beauty means revealing the areas of beauty. The wrists, ears, neck, feet are all included in this. These are called the areas of beauty i.e. the areas from where beauty is expressed.
As far as the non-Mahram are concerned, if there is any fear of any corruption, then the whole body and even the face should be covered. If there is no such fear, then there is no problem in keeping the face and palms uncovered. As said by Allah (Subhanahu Wa Ta'ala):
……….that they should not display their beauty and ornaments except what (ordinarily) appear thereof;
As given in Hidayah in Kitabul Karahiya, Pg No: 452:
Translation: According to Hadhrat Ali and Hadhrat Ibn Abbas (May Allah be well pleased with them) that except “what (ordinarily) appear thereof” means the Kohl of the eyes and the ring.
There is a Hadith in Sunan Abu Dawood, Hadith No. 3580:
Translation of Hadith: Hadhrat Asma bin Abu Bakr (May Allah Ta'ala be well pleased with him) came to the Holy Prophet (Sallallahu alaihi wa sallam) and she was wearing very thin and fine clothes and the Holy Prophet (Sallallahu alaihi wa sallam) turned His head away and said: O Asma! When a girl matures, it is not advisable that her parts of body should be revealed except this and He pointed towards His face and His palms.