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.
  is His slave and Messenger.
The mothers of the believers did not reveal their faces; rather, they used to cover them.
Ibn Hajar  said in his book [Fat’h al-Baari, Sharh saheeh al-Bukhari], quoting al-Qadi ‘Iyad: “The Hijab was ordained on them without any difference of opinion to cover their faces and hands, so it is not permissible for them to reveal that when giving testimony [in front of judge, if required], or in other matters.” [End of quote.]
  said in his book [Fat’h al-Baari, Sharh saheeh al-Bukhari], quoting al-Qadi ‘Iyad: “The Hijab was ordained on them without any difference of opinion to cover their faces and hands, so it is not permissible for them to reveal that when giving testimony [in front of judge, if required], or in other matters.” [End of quote.]
We have already mentioned in Fatwa  ’s wives">115107 that the Niqab was the dress of the wives of the Prophet  but it was not peculiar to them; rather, this is for all the believing women.
  but it was not peculiar to them; rather, this is for all the believing women.
Allah knows best.