AsalamuALaykum Warahmatullahi Wabarakatuh,
Narrated 'Aisha
(the wife of the Prophet) 'Umar bin Al-Khattab used to say to Allah's Apostle "Let your wives be veiled" But he did not do so. The wives of the Prophet used to go out to answer the call of nature at night only at Al-Manasi.' Once Sauda, the daughter of Zam'a went out and she was a tall woman. 'Umar bin Al-Khattab saw her while he was in a gathering, and said, "I have recognized you, O Sauda!" He ('Umar) saidso as he was anxious for some Divine orders regarding the veil (the veiling of women.) So Allah revealed the Verse of veiling. (Al-Hijab; a complete body cover excluding the eyes). (See Hadith No. 148, Vol. 1)
Surah Al-Ahzaab, Verse #59
O Prophet! Tell your wives and your daughters and the women of the believers to draw their cloaks ("Jalabib") veils all over their bodies (screen themselves completely except the eyes or one eye to see the way Tafseer Al-Qurtabi) that is most convenient that they should be known (as such) and not molested: and Allah is Oft-Forgiving Most Merciful."
Surah An-Nur, Verses #30 and #31
And Say to 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, head cover, apron), and to draw their veils all over Juyubihinna (i.e. their bodies, faces, necks and bosoms)
Sahih Al-Bukhari Volume 6, Book 60, Hadith # 282
Narrated Safiya bint Shaiba (Radhiallaahu Ánha) "Aisha (Radhiallaahu Ánha) used to say: "When (the Verse): "They should draw their veils over their necks and bosoms," was revealed, (the ladies) cut their waist sheets at the edges and covered their faces with the cut pieces.
"Imam Shafi, Malik and Hanbal hold the view that niqaab (covering the faceand the hands completely with only a small area for the eyes to see) as being compulsory (fard). Imam Abu Hanifa says that niqaab is Wajib and the face and hands can be exposed provided that there is not fear of desire if one looks at the female face, otherwise if there is the slightest chance of desire developing in the looker (the meaning of desire is that the looker would see the female face and think that she is beautiful, sexual thought is not what is meant) then exposing the face and hands is Haraam.
Peace.