Is it permissible for my wife to expiate her vow to wear the niqab if we are blessed with a child, given her work as a teacher for the deaf and mute, where women who wear the niqab are prohibited from teaching in schools?

The niqab is obligatory for women and it is not permissible to abandon it. The aforementioned wife should promptly wear it without the need for a vow, because the niqab is a religious obligation. Her fears regarding difficulties at work do not justify abandoning the niqab, for sustenance is in the hands of Allah. Allah has guaranteed to those who fear Him that He will open doors of provision for them. Allah Almighty says: (And whoever fears Allah – He will make for him a way out And will provide for him from where he does not expect). And sustenance is decreed; no soul will die until it has received its full provision.

Regarding the vow, scholars have differed concerning it. The majority view is that it is not binding, because it is an commitment to what is already obligatory. Others held it to be binding, and this was preferred by Shaykh al-Islam Ibn Taymiyyah. According to this view, expiation is incumbent upon anyone who does not fulfill it.