Is the Niqab obligatory?
There are some difference of opinion regarding the obligation of the Niqab in Islam. The correct view is that the face must be covered and that it belongs to the 'awrah of a Muslim woman. That is the view of Ahmad ibn Hanbal, Shafi'i and Malik ibn Anas.
The proofs cited are verses from the Quran with the interpretation of the Sahaba and Tabi'een. How the Niqab began is as follows:
'Umar reported:
"I said: 'O Messenger of Allah. Good and bad persons enter your house, so I suggest that you order the mothers of the believers (i.e. your wives) to wear veils."
Then Allah revealed the verses of Al-Hijab (covering).
Sahih al-Bukhari 4790
O Prophet! Ask your wives, daughters, and believing women to draw their cloaks over their bodies. In this way it is more likely that they will be recognized ˹as virtuous˺ and not be harassed. And Allah is All-Forgiving, Most Merciful.
(Surah al-Ahzab verse 59)
Here we see that the companion 'Umar was a reason that the women should cover their faces. 'Umar is unique in this quality of encouragement.
When the verses came regarding the face veil, the Sahabiyat immediately began to apply it. From this we see how they understood and applied those verses.
'Aisha said:
"May Allah have mercy on the wives of the Muhaajireen. When Allah revealed the Words: "and to draw their Khumur (veils) over Juyoobihinna (i.e. their bodies, faces, necks and bosoms)" [Surah Al-Nur verse 31] they tore their waste sheets and covered their faces with them."
(Sahih al-Bukhari 4480)
Tafsir of the verses about Niqab
Ibn 'Abbas (Sahabi) said:
"God commands the wives of the believers, when they go out of their houses in need, that they cover their faces with a veil, and uncover one eye."
[Tafsir Ibn Abi Hatim, 10/3155]
Muhammad ibn Sirin (Tabi'i) said:
"I asked 'Ubaida bin Abu Sufyan bin al-Harith about the saying of Allah Almighty: 'to put on some of their jalabīb (outer garments)." [Surah al-Ahzaab verse 59], so 'Ubaidah demonstrated covering it by covering his face and head, and exposing his left eye."
[Tafsir Ibn Abi Hatim, 10/3155]
Yahya ibn Sallaam (Mufassir, died in 200 Hijri) said:
"{O Prophet, tell your wives and daughters and the wives of the believers to put on a part of their jalabīb (outer garments)} means the Jilbab covering the face and leaving the left eye uncovered."
[Tafsir of Yahya ibn Sallam 2/738]