Is a Woman's Face `Awrah?
Question

With regard to the Niqab, what are the Hadiths and verses that refer specifically to it
Praise be to Allah.The correct view is that a woman is obliged to cover her entire body, even the face and hands . Imam Ahmad said that even the nails of a woman are `Awrah, and this is also the view of Malik (may Allah have mercy on them both).
Shaykh Al-Islam Ibn Taymiyah (may Allah have mercy on him) said:
“… It seems that the view of Ahmad is that every part of her is `Awrah, even her nails, and this is also the view of Malik.” (Majmu` Al-Fatawa, 22/110)
Analyzing Views against Face Veiling in Islam
In contrast to those who say that this is not obligatory , if we examine the views of those who say that it is not obligatory for women to cover the face, we will see that it is as Shaykh Bakr Abu Zayd (may Allah preserve him) said:
“One of the following three scenarios must apply:

There is clear, sound evidence, but it has been abrogated by the verses that enjoin Hijab…
There is sound evidence but it is not clear, and it does not constitute strong evidence when taken in conjunction with the definitive evidence from the Quran and Sunnah that the face and hands must be covered …
There is clear evidence, but it is not sound…” (Hirasat Al-Fadilah, p. 68-69)

Evidence from the Quran on Covering the Face and Hands
With regard to the evidence that it is obligatory to cover the face and hands :

Allah says (interpretation of the meaning):

{O Prophet! Tell your wives and your daughters and the women of the believers to draw their cloaks (veils) all over their bodies (i.e. screen themselves completely except the eyes or one eye to see the way). That will be better, that they should be known (as free respectable women) so as not to be annoyed. And Allah is Ever Oft-Forgiving, Most Merciful.} [Al-Ahzab 33:59]
Ibn Taymiyah (may Allah have mercy on him) said:
“Allah commands women to let the jilbab come down (over their faces) so that they will be known (as respectable women) and not be annoyed or disturbed. This evidence supports the first opinion. `Ubaydah As-Salmani and others stated that the women used to wear the Jilbab coming down from the top of their heads in such a manner that nothing could be seen except their eyes, so that they could see where they were going. It was proven in As-Sahih that the woman in Ihram is forbidden to wear the Niqab and gloves. This is what proves that the Niqab and gloves were known among women who were not in Ihram. This implies that they covered their faces and hands.” (Majmu` Al-Fatawa, 15/371-372)

Allah says (interpretation of the meaning):

{And tell the believing women to lower their gaze (from looking at forbidden things), and protect their private parts (from illegal sexual acts) and not to show off their adornment except only that which is apparent (like both eyes for necessity to see the way, or outer palms of hands or one eye or dress like veil, gloves, headcover, apron), and to draw their veils all over Juyoobihinna (i.e. their bodies, faces, necks and bosoms)…” [An-Nur 24:31]
Shaykh Al-Islam Ibn Taymiyah (may Allah have mercy on him) said:
“With regard to the phrase ‘and not to show off their adornment except only that which is apparent’,  `Abdullah ibn Mas`ud said: the adornment which is apparent is the garment, because the word Zinah (adornment) was originally a name for the clothes and jewellery, as we see in the verses in which Allah says (interpretation of the meaning):
{Take your adornment (by wearing your clean clothes.)} [Al-A`raf 7:31]
{Say (O Muhammad): Who has forbidden the adornment with clothes given by Allah, which He has produced for His slaves.} [Al-A`raf 7:32]
{And let them not stamp their feet so as to reveal what they hide of their adornment.} [An-Nur 24:31]
Stamping the feet makes known the Khulkhal (anklets) and other kinds of jewellery and clothing. Allah forbade women to show any kind of adornment except that which is apparent, but He allowed showing the hidden adornment to Mahrams. It is known that the kind of adornment that usually appears, without any choice on the part of the women, is the clothing, as for the body, it is possible to either show it or to cover it. All of this indicates that what appears of the adornment is the clothing.
Ahmad said: the adornment which is apparent is the clothing. And he said: every part of a woman is `Awrah, even her nails. It was narrated in the Hadith, ‘The woman is `Awrah,’ This includes all of the woman. It is not disliked to cover the hands during prayer, so they are part of the `Awrah, just like the feet. Analogy implies that the face would be `Awrah were it not for the fact that necessity dictates that it should be uncovered during prayer, unlike the hands.” (Sharh Al-`Umdah, 4/267-268)
Hadith Supporting Face Veiling in the Presence of Non-Mahrams

It was narrated that `Aishah said: “The riders used to pass by us when we were with the Messenger of Allah (peace and blessings of Allah be upon him) in Ihram. When they came near, each of us would lower her Jilbab from her head over her face, and when they passed by we would uncover (our faces).” (Narrated by Abu Dawud, 1833 and Ahmad, 24067)

Shaykh Al-Albani said in Jilbab Al-Mar’ah Al-Muslimah (107): its chain of narration is sound because of the existence of corroborating reports.
It is well known that a woman should not put anything over her face when she is in ihram, but `Aishah and the female Companions who were with her used to lower part of their garments over their faces because the obligation to cover the face when non-Mahrams pass by is stronger than the obligation to uncover the face when in ihram.

It was narrated that `Aishah (may Allah be pleased with her) said: “May Allah have mercy on the women of the Muhajirin. When Allah revealed the words (interpretation of the meaning): {and to draw their veils all over Juyubihinna (i.e. their bodies, faces, necks and bosoms)…} [An-Nur 24:31], they tore their aprons and covered their faces with them.” (Narrated by Al-Bukhari, 4480)
It was narrated from `Aishah… that Safwan ibn Al-Mu`attal As-Sulami Adh-Dhakwani was lagging behind the army. He came to where I had stopped and saw the black shape of a person sleeping. He recognized me when he saw me, because he had seen me before Hijab was enjoined . I woke up when I heard him saying ‘Inna Lillahi wa inna ilayhi raji`un (verily to Allah we belong and unto Him is our return),’ when he saw me, and I covered my face with my Jilbab.” (Narrated by Al-Bukhari, 3910 and Muslim, 2770)

It was narrated from `Abdullah that the Prophet (peace and blessings of Allah be upon him) said: “The woman is `Awrah  and when she goes out the Shaytan gets his hopes up.” (Narrated by At-Tirmidhi, 1173)
Al-Albani said in Sahih At-Tirmidhi (936): It is authentic.
And Allah knows best.