Is the niqab neither an obligation nor a sunnah, but merely a virtue for which there is no reward for doing it and no sin for abandoning it, and will the one who wears it not be rewarded for emulating the Mothers of the Believers?

The niqab, with which a woman covers her face, is an issue where scholarly disagreement among the jurists is confined to whether it is religiously obligatory or recommended. However, there is no disagreement regarding the reward for wearing it.