Can a widow wear niqab during her ʿiddah?
Yes. One Ḥanbalī authority held otherwise, but his own school records that as his individual position: the sound view of the school permits it.
The restriction
Imam al-Khiraqī (d. 334 H) held that a woman in mourning for her husband should avoid perfume, adornment, spending the night elsewhere, kohl of ithmid, and the niqab. If she needed to cover her face, she should let a cloth down over it as a woman in iḥrām does, until her waiting period ends.
Why it does not stand as the school's position
The majority of Ḥanbalī scholars did not accept it, and recorded it as al-Khiraqī's personal view. Al-Mardāwī's statement above is explicit; the detail that matters is the one easy to read past: the sound position of the school is not just what its scholars settled on, it is what Imam Aḥmad himself stated by text. That is a stronger claim than a later consensus; it says the founder's own words run this way.
This is among the things al-Khiraqī said alone. He was followed in it by Ibnu Ḥamdān in al-Riʿāyatān, by ʿAbd al-Raḥmān al-Ḍarīr in al-Ḥāwī, and by a group of the school. The sound position of the school, settled upon by its scholars, is otherwise.
Qāḍī Abū Yaʿlā does transmit something similar from Imam Aḥmad in the other direction — that he disliked the niqab for a widow, though not for a divorced woman. But al-Mardāwī has already said Aḥmad's own text runs the other way, so this is not a live counterweight to it.
Even if Abū Yaʿlā's transmission is sound, the position it records remains anomalous and is not the one known to the majority.
In practice
A widow may wear niqab during her ʿiddah. The alternative — letting a cloth down over the face, as in iḥrām — remains available to anyone who prefers to follow al-Khiraqī's caution.
Check your understanding
Imam al-Khiraqī held that a widow in mourning should avoid wearing niqab during her ʿiddah. What is the Ḥanbalī school's actual position, according to the note?