Muslim women have guidelines on dress code from the Shariah. The niqab is not a requirement; it is a custom of some Muslims. Allah سُبْحَانَهُ وَ تَعَالَى Says:
“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 headcovers 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” (Surat an-Nur, verse 31, translation by Sahih International).
This verse instructs:
(1) Lowering the gaze, not staring at people, not looking with lust at others – to be modest and shy. The habit of keeping your head down is a display of the moral virtues of modesty and shyness.
(2) Physically covering natural beauty. This includes the hair, the neck and the breasts.
The Quran is teaching Muslim women to adopt a particular attitude and behaviour, to be modest and to dress modestly. Most traditional commentators have concluded from this verse and verse 59 of Surat al-Azhab that the niqab (covering of the face) is not included in this, except for Ibn Kathir, who thinks niqab is necessary.
“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” (Surat al-Azhab, verse 59, translation by Sahih International).
It is interesting to note that some commentators present their own support for the niqab after giving the Shariah ruling on women’s dress code. However, they make it absolutely clear that this is a personal preference (see ‘Zia ul Quran’ and ‘Tafsir Usmani’).