Amina Inloes, Amina Inloes is originally from the US and has a PhD in Islamic Studies from the University of Exeter on Shi'a hadith. She is the program leader for the MA Islamic Studies program at the... Answer updated 1 year ago

There is no evidence that the wives of the Prophet (S) or Fatimah al-Zahra (A) covered their faces.

Face-covering (niqab) became common among Muslims around or after the time of the caliphate of Imam 'Ali in Kufa, and so it seems reasonable that his daughters and those who came after them covered their faces since this was a social norm then at that time, at least for women of certain social classes. 

(This is of course based on historical records we have of that time, and God knows best.)