Allah The Almighty prescribed in His Book as well as in the guidance of His Prophet, sallAllahu ‘alayhi wa sallam, what safeguards women. Allah The Almighty prescribed the Hijab (Islamic covering) for the Muslim woman. Hijab means chastity, purity, exaltation of position, covering, veneration, keeping away from doubt and thoughts of lewdness and adultery and warding off the lusts of people who have sick hearts for chaste and pure women. Therefore, along with the Hijab, Allah prescribed the etiquette of speech and forbade using a soft tone in speech to close the door before any feelings of lust are aroused in the hearts of those who are misguided and deviated.
Allah The Exalted Says (what means): {And tell the believing women to reduce [some] of their vision and guard their private parts and not expose their adornment except that which [necessarily] appears thereof and to wrap [a portion of] their veils over their chests and not expose their adornment except to their husbands, their fathers, their husbands' fathers, their sons, their husbands' sons, their brothers, their brothers' sons, their sisters' sons, their women, that which their right hands possess, or those male attendants having no physical desire, or children who are not yet aware of the private aspects of women. And let them not stamp their feet to make known what they conceal of their adornment. And turn to Allah in repentance, all of you, O believers, that you might succeed.} [Quran 24: 31]
Commenting on the verse, Al-Qurtubi said, "It is impermissible for a woman who believes in Allah and the Last Day to expose her adornment except for her husband as well as her Mahram (non-marriageable) men. A Mahram man will not have sexual desire for her because he knows that she is permanently forbidden for him."
The Sharee‘ah (Islamic legislation) gives strict orders in terms of safeguarding the woman and protecting her from her non-Mahram men even if they are her in-laws. It was narrated on the authority of ‘Uqbah ibn ‘Aamir, may Allah be pleased with him, that the Messenger of Allah, sallAllahu ‘alayhi wa sallam, said: "‘Do not enter upon women.’ A man of the Ansaar asked, ‘O Messenger of Allah, what about the (brother) in-law?’ The Prophet, sallAllahu ‘alayhi wa sallam, replied: ‘The in-law is death.’ " [Al-Bukhari]
In Al-Mufhim, Al-Qurtubi commented,
(The in-law is death) means that when the in-law enters upon the woman and remains with her in seclusion, this is similar to death in terms of rejection and corruption. This is strictly forbidden. The forbiddance is strictly reported concerning in-laws, as it is likened to death, because people usually take it easy as if he is one of the woman's Mahrams. This way of expression is similar to the Arabs' saying: "The lion is death" and "War is death." This means that meeting the lion and fighting leads to death. Similarly, when the in-laws enter upon the woman, this could lead to death of the religion or lead to her own death through either divorce in case the husband is taken by jealously or stoning to death in case of committing adultery.
Commenting on the rest of the verse, Al-Qurtubi said, "Allah The Almighty commands women not to expose their adornment before men, except those who are mentioned in the rest of the verse. This is to avoid temptation. Then He made an exception of that which necessarily appears from the adornment. There is a difference among Muslims regarding the extent of the part of the adornment that is exempted from the prohibition. Ibn Mas‘ood, may Allah be pleased with him, said, ‘The apparent adornment is clothing. (Others, however, have stated otherwise)’".
Ibn ‘Atiyyah said, "Based on the wording of the verse, it seems that the woman is required not to display any of her adornment and to exert her best to conceal it. The exception, however, is reported concerning that which necessarily appears from the adornment, because of moving, mending something and so on. The part which necessarily appears from the woman' adornment is excused."
Al-Qurtubi said, "There are two types of adornment: natural and acquired. The natural adornment is her face as it is the origin of adornment and beauty. The acquired adornment is that which a woman tries to apply to her body to beautify herself, such as clothing, jewelry, kohl and henna. This last type is intended in the verse in which Allah The Exalted Says (what means): {O children of Adam, take your adornment at every Masjid…} [Quran 7: 31]”
He added, "Some adornments are apparent and others are not. It is permissible to display the apparent adornment before all people, whether they are Mahrams or not. However, it is impermissible to display the hidden adornment except before those whom Allah mentioned in the verse as well as those who are in the same degree (Mahrams). Ibn Al-‘Arabi said, 'When henna is applied to feet, it is a part of hidden adornment.'"
(To wrap [a portion of] their veils over their chests) : The reason behind revealing this verse is that during that era women used to wear the veils lowering their ends on their backs. An-Naqqaash said,
It was the habit of the Nabt farmers (who lived in the part between the Arabia and Ash-Shaam area). They used to leave the upper part of the chest, the neck and the ears uncovered.
Therefore, Allah The Almighty commanded that the veil should be dropped over the chests. The woman draws her veil over her chest to cover it. ‘Aa’ishah, may Allah be pleased with her, said, "May Allah have mercy on the early women from among the Muhaajiroon (Emigrants). When the verse: {wrap [a portion of] their veils over their chests} was revealed, they tore their thick outer garments and made veils from them." [Al-Bukhari]
It was also narrated that the niece of ‘Aa’ishah, may Allah be pleased with her, Hafsah bint ‘Abdul-Rahmaan, may Allah be pleased with her, entered upon her veiled with transparent clothes which showed her neck and other parts. Thereupon, ‘Aa’ishah, may Allah be pleased with her, tore it upon her, and said, "The veil must be from thick clothes which cover."