Is wearing the niqab obligatory, and what is the verse that indicates its obligation, and what is the punishment for not wearing it?

Scholars have differed regarding the ruling on a woman covering her face in front of non-mahram men. The preponderant opinion is the obligation to cover the face with any covering, whether with the niqab or by letting down the khimar. Even if covering the face were not obligatory by default, it becomes obligatory if the father commands it, because obedience to parents is obligatory in matters that do not involve disobedience. The scholars' disagreement about the obligation of covering does not mean that the ruling was unclear or not practiced during the era of prophethood.