All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
The Muslim scholars have different opinions over this matter, i.e. whether or not a woman should cover her face and palms before non-Mahram (marriageable) men.
According to the Hanbali School of jurisprudence, and the correct view of the Shaafi'i School, she should cover her face and palms before non-Mahram men, since they are an ‘Awrah (parts of the body that should be covered in Islam).
But the Hanafi and Maaliki Schools do not consider them as an ‘Awrah.
On the other hand, the Hanafi and Maaliki Schools affirm their view since a long time that a Muslim woman should cover her face and palms as long as there is a risk of temptation. The temptation means if a woman is beautiful or if immorality is common, or unchaste people are widespread.
Therefore, covering the face and palms is the preponderant viewpoint according to the correct opinion of the four Schools. So, uncovering the face would be considered a kind of unveiling.
There is much evidence in the Quran and Sunnah that proves that covering the whole body is compulsory. Some of them are as follows:
1 - Allah Says (what means): {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.} [Quran 33:59]
Most interpreters of the Quran established that this verse indicates that covering the face is compulsory because the "Jilbaab" [i.e. the Arabic word used in the verse] means a loose garment which is used to cover the head, and covers the face when it is lowered.
It is also said that Jilbaab means the garment, which covers the whole body. This was also confirmed by Imam al-Qurtubi.
As regards the verse in Surah an-Noor, in which Allah Says (what means): {…and not expose their adornment except that which [necessarily] appears thereof.} [Quran 24:31]; it means the external garment and this is the most correct opinion. This is narrated also from Ibn Mas’ood, may Allah be pleased with him. Or it means what becomes uncovered without any intention. For example, what is caused by wind or the like.
2 -The verse about Hijaab: {And when you ask [his wives] for something, ask them from behind a partition. That is purer for your hearts and their hearts.} [Quran 33:53]
The purity, which is mentioned in this verse, is not peculiar to the mothers of believers. But every Muslim woman is in need of it. In fact, Muslim women are more in need for this order than the wives of the Prophet .
3 -Allah Says in Surah an-Noor (what means): {…and to wrap [a portion of] their head covers over their chests….} [Quran 24:31]
Imam Al-Bukhaari narrated from ‘Aa’ishah : “When (the verse) {…and to wrap [a portion of] their head covers over their chests….} was revealed, (the ladies) cut their waist-sheets from their margins and covered their heads and faces with those cut pieces of cloth.”
Imam Ibn Hajr said: "They covered their faces."
Imam at-Tirmithi narrated from Abu Hurayrah that the Prophet Muhammad said: "A woman is an ‘Awrah; when she gets out, Satan makes people to look at her."
This is evidence that the whole body of the woman is an ‘Awrah.
Ibn Umar narrated that the Prophet Muhammad said: "A pilgrim woman must neither cover her face nor wear gloves in the state of Ihram."
Imam Abu Bakr Ibn al-‘Arabi said: “It is compulsory on the woman to cover her face except in Hajj. Therefore she should let down her scarf on her face without letting it stick directly to her face and should turn away from men.” [Excerpted from Arizatul-Ahwathi's book]
‘Aa’ishah said: "Men on camels used to pass by us while we were with the Prophet Muhammad in the state of Ihram. We would cover our faces with our gowns when they passed by us, and then uncover them again (when they had gone far from us)."
Allah knows best.