Is wearing the niqab obligatory, and is it obligatory in this time, and what is the opinion of Imam Ibn Taymiyyah and the Four Imams on that?

The scholars of the four Madhhabs (schools of thought) agreed on the obligation for a woman to cover her face when people are corrupt and their religious deterrence is weak. They differed on the ruling of covering it if people are righteous. Sheikh al-Islam Ibn Taymiyyah concurs with their agreement, as Ibn Muflih narrated from him that it is not permissible for women to uncover their faces in a way that allows non-mahram men to see them.