The ex-husband dies during his divorcee's waiting period
A woman was divorced from her husband who passed away during her post-divorce ‘idda (waiting period a woman is to observe before she is allowed to remarry). Which ‘idda should she observe—the post-divorce ‘idda or the one for a deceased husband?
If a man gives his wife a revocable divorce (in which he can take her back before the ‘idda expires), and subsequently passes away while she is in her ‘idda, the post-divorce’ idda is waived and she is to start her ‘idda for a deceased husband which lasts for four months and ten days from the day of her husband’s death. This is because a woman who is given a revocable divorce is still considered a wife for the entire time she is in her ‘idda and the following verse applies to her, “And if any of you dies and leave widows behind; they shall wait concerning themselves four months and ten days” [2:234].
If a woman is irrevocably divorced and her husband dies afterwards, she is to continue her post-divorce ‘idda. In such a case, her husband’s death has no bearing on the ‘idda since the marriage bond has been severed by the irrevocable divorce, whether it is a minor or a major irrevocable divorce. Imam Al-Nawawi (may Allah have mercy on him) wrote in Rawdat Al-Talibeen (vol. 8, p. 399), “If a man dies while his wife is in her post-divorce ‘idda and the divorce was revocable, the post-divorce ‘idda is waived and she is to observe the ‘idda for a deceased husband to mourn her deceased husband; she is not eligible for nafaqa. But if her husband had divorced her with an irrevocable divorce, she is to complete her post-divorce ‘idda and is eligible to receive nafaqa if she is pregnant.”
Allah the Almighty knows best.