Ive been summoned.
There are two views with regards to Niqab : Obligatory and highly recommended. They both have significant proofs. I will just highlight that Niqab is from Islam.
Allah says:
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.
Abdullah ibn Abbas explained this verse saying: "Allah commanded the believing women to cover their faces from above their heads with the jilbaab, leaving only one eye showing, when they went out of their houses for some need."
And the tafseer of a companion is a proof. Indeed, some of the scholars have said that it bears the ruling of a statement attributed to the Prophet. As for Ibn Abbas statement: "... leaving only one eye showing," this was only permitted for necessity in order to see the way. But if there is no need, then it is not necessary to reveal an eye. As for jilbaab, it is a loose cloak worn over the khimaar in the place of the Aba'ah. Umm Salamah said that when the verse was revealed "the women of the ansar went out as if they had crows on their heads, due to their piety and they were wearing black cloaks."
Ubaidah as Salami and others have stated that the wives of the believers used to draw their cloaks around them above their heads, so that nothing could be seen except their eyes, and this was in order for them to see the way.
[Sheikh Ibn Uthaymeen, A treatise on hijab,p.17]
Sheikh Al Abani writes:
Know that covering of the face and the wrists has its basis in the sunnah. And this was an action that was done during the time of the Prophet as is shown by his statement narrated by Bukhari:
"The women in the state of ihraam should not wear a niqaab, nor should she wear gloves."
...
Sheikh Al Islaam Ibn Taymiyyah in his tafseer of soorat un noor said:
And this is what shows that the niqaab and the gloves used to be something common for the women who were not in the state of Ihraam, and from this also is a basis for the legality of covering the face and the wrists. [Majmoo' al fatawa (15/276)]
[Sheikh Al Albani, Jilbaab Almaraat al muslimat, p.64]
Sheikh Ibn Uthaymeen writes:
It is reported on the authority of 'Aishah that she said "The riders used to pass by us while we were in a state of Ihraam with the messenger of Allah. Whenever they came close to us, each of us would let her jilbaab fall from her head so that it covered her face, then once they had passed us, we would uncover our faces." [Imam Ahmad (24522), Abu Dawood (1833)]
Her words: "... and whenever they came close to us, each of us would let her jilbab fall her head so that it covered her face." is proof that it is obligatory for a woman to cover her face, because it is legislated during ihraam for a woman to uncover it. If there was no strong prohibition for covering at that time, they would have left their faces uncovered. This is because uncovering the face during ihram is obligatory for women, according to the majority of scholars - and an obligation cannot be contradicted,except by another obligation. Therefore, if it was not obligatory to veil and cover the face from unrelated men, it would not be permissible to abandon the obligation to uncover the face while in a state of ihraam.
[Sheikh Ibn Uthaymeen, A Treatise on Hijab, p.24]