All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
It is not correct to say that the order to cover the face is peculiar to the wives of the Prophet because there is evidence that this ruling applies to all Muslim women; the following is the evidence about this:
1- Allaah 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.}[Quran 33:59] Many interpreters of the Quran determined that the verse means an order to cover the face and this is the view which is considered to be correct by Imaam Al-Qurtubi. Moreover, this verse applies to all the believing women.
2- Allaah Says (what means): {… and to wrap [a portion of] their head covers over their chests.}[Quran 24:31] Imaam Al-Bukhari reported that ‘Aaishah said: “When this verse was revealed, they (the female women companions) cut their waist sheets at the edges and covered their faces with the cut pieces.”
3- Allaah Says (what means): {…And when you ask (his wives) for anything you want, ask them from behind a screen, that is purer for your hearts and for their hearts…}[Quran 33:53] This purity is not specific to the mothers of the believers but this is something that is needed by all the believing women. Rather, it is more appropriate that the ruling applies to all other women than the pure and innocent mothers of the believers.
4- Ibn ‘Umar narrated that the Prophet said: “A woman in a state of Ihraam should not wear Niqaab (face covering) or gloves.” [Al-Bukhari] Abu Bakr ibn Al-‘Arabi said: “That is because covering her face with a veil is an obligation except during Hajj when she should only lower some of her Khimaar (head covering) over her face but not something that is fitted over her face, and she should avoid men (seeing her face) and they should avoid seeing her (face).” His statement means that covering the face is not only a legislated act but an obligation on a Muslim woman, and this is the preponderant opinion in our view in Islamweb.
For more benefit please refer to Fataawa 83033 and 81554.
Allaah Knows best.