In answer to questions about whether the niqab is obligatory for Muslim women:
The respected Egyptian scholar Yusuf al-Qaradawi has done a detailed study of the evidence regarding the niqab, published as al-Niqāb Bayna Farḍīyatih wa Bidʿīyatih1, and his conclusion is that the niqab is neither a duty, nor is it a bidʿa (false innovation) to be condemned, it is rather a tool, an item of clothing, that a woman chooses to wear if and when she wants. If a woman sees that it is beneficial for her to wear it in her particular time and place, then she can do it. And if other women elsewhere decide not to wear it, like the majority of Muslim women have decided, then that’s their choice. There is nothing wrong with a woman veiling her face at a certain occasion, the way Victorian women used to, if she decides that she is more comfortable that way and expects benefits from it.
Dr. Ali Gomaa, Grand Mufti of Egypt from 2003 to 2013, has the same opinion.2 Egypt’s present Grand Mufti Dr. Shawki Allam says the same.3 This is also the opinion of Sheikh Ahmed el-Tayeb, Grand Imam of Al-Azhar University.4 He says the the niqab is not a sunna and that there is no special virtue in wearing it.
The Syrian scholar Dr. ʿAli al-Shaʿʿāl says it is not obligatory.5
Sheikh Muhammad Ahmad Hussein, Grand Mufti of Jerusalem, also has the opinion that the niqab is not obligatory.6
The above are just some examples of the opinions of mainstream Islamic scholars. They represent the opinions of the majority of Muslims. There is also no strong evidence that the niqab is a sunna either, something that Muslim women should supposedly hope to one day wear. Neither the Quran nor any hadith recommend that women should wear it. The niqab, like sandals and water containers made of goat skin, is something that was present in medieval Arabia, it was part of their culture and had a useful function at the time, which was to help women avoid the attention of uncouth men who would make them uncomfortable through ogling. As someone who has traveled a bit, I have met such men in some Middle Eastern countries. If even a slightly attractive woman comes into their field of view, they will stare at her, and stare, and stare, as if watching a TV program. That objectifying gaze is extremely uncomfortable and demeaning for a woman, so if she lives in a society where she is unlucky enough to face such men often, then it would be beneficial for her to have a niqab handy.
But in a civilized, middle class society where the men do not act like that, there is little point to the niqab. Whether one should wear niqab or not should be judged according to its potential benefits and harms and one’s own present time and culture. Just because we have reports of the people of that time doing some thing does not automatically mean it is recommended for us to do it. Thinking the niqab is recommended just because some women in medieval Arabia wore it is probably similar to thinking that hanging water containers made of goatskin in the living room, as the Prophet did, is somehow virtuous. A sunna, or virtuous act taught by the Prophet , can only be established when we have clear and multiply-verified evidence that the Prophet recommended that act. But we have no such evidence. As al-Qaradawi mentions, we have numerous authentic hadiths in which Muslim women are mentioned as showing their faces in public, and we have no convincing evidence that that Prophet would have liked them to hide their faces, even as a voluntary act of piety.
A woman who wishes to hide her face as a personal act of piety can certainly be rewarded for it, but it would be wrong if she said it is a sunna. Not every good deed is a sunna. For example if you choose to donate 5% of your income to charity, we have no evidence that the Prophet did the same or recommend that we do this, but you can do it with a good intention and get rewarded for it.
Those who say the niqab is obligatory are often converts or people who know little about Islam and who are now trying to be good Muslims. They sometimes come under the influence of Saudi-funded websites like IslamQA.info and due to their lack of knowledge end up thinking that these websites represent some true or authentic version of Islam. And due to the way that these websites teach their followers to think of themselves as the only true Muslims, they end up looking down on everyone else and try to force their opinions on them. Usually after a few years of crusading against mainstream Muslims they either abandon Islam (since they can no longer live with themselves) or they become moderate as their knowledge increases.
For more about Saudi-funded sites see my article about IslamQA.info.