All perfect praise be to Allah, The Lord of The Worlds, and may His peace and blessings be upon our Prophet Mohammad and upon all his family and companions.
Islam has commanded women to guard their modesty, and this is clearly stated in many texts, such as: " And say to the believing women that they should lower their gaze and guard their modesty; that they should not display their beauty and ornaments except what (must ordinarily) appear thereof; that they should draw their veils over their bosoms " {An-Noor/31}. Allah, The Almighty also Says: "O Prophet! Tell thy wives and daughters, and the believing women, that they should cast their outer garments over their persons (when abroad): that is most convenient, that they should be known (as such) and not molested. And God is Oft- Forgiving, Most Merciful." {Al-Ahzab/59}. This verse indicates that guarding modesty is a means of protecting women.
As for covering the face, Muslim jurists have disagreed about this point; some say it is obligatory while others consider it preferable, but there is no doubt that it is part of the Prophet's wives and the Sahabiyat`s clothes. Therefore, a woman who wears the Niqab is on the safe side as far as the teachings of Sharia are concerned and is cleared from liability before Allah, The Almighty. And Allah Knows Best.