The general understanding in Islam regarding Sunnah, is that if the Prophet or any of his wives (RA) or companions (RA) are recorded in authentic hadith to have engaged in an act that is not haram (prohibited) as defined by Qur’an or Sunnah, then the act is declared halal (permissible). If the companions engaged in an act that the Prophet was aware of and did not speak out against, it is halal.
It is well-known that the wives of the Prophet covered their faces any time non-mahram men were near. A woman named Asma, who was not a wife of the Prophet , was also recorded as covering her face. Easily, one can conclude that wearing veil is halal (permissible).
However, Muslims and Muslimahs across the world have been in “hot debate” for centuries, over the issue of whether or not covering the face is obligatory upon a Muslimah. Those who argue that it is not required, point to the use of the word khimar in the Qur’an, and explain that today’s modern khimar does not cover the face, and argue that khimar has never referred to the covering of the face, but only to that of the hair, neck, and bosoms. While one cannot deny the support of Hadith that indicate that the Prophet’s wives wore khimar, one must realize that they also covered their faces at all times in the presence of non-mahram men.
The group of scholars agree that it is a highly recommended act to cover the face. The scholars also agree that a woman must cover her adornment, yet some scholars argue that this does not include the face.