That ʿAbdullah bin ʿUmar told him that he had divorced his wife while she was in her menses so ʿUmar informed Messenger of Allah ﷺ of that. Messenger of Allah ﷺ became very angry at that and said, "(Ibn ʿUmar must return her to his house and keep her as his wife till she becomes clean and then menstruates and becomes clean again, whereupon, if he wishes to divorce her, he may do so while she is still clean and before having any sexual relations with her, for that is the legally prescribed period for divorce as Allah has ordered."  

أَخْبَرَهُ أَنَّهُ طَلَّقَ امْرَأَتَهُ وَهْىَ حَائِضٌ فَذَكَرَ عُمَرُ لِرَسُولِ اللَّهِ ﷺ فَتَغَيَّظَ فِيهِ رَسُولُ اللَّهِ ﷺ ثُمَّ قَالَ لِيُرَاجِعْهَا ثُمَّ يُمْسِكْهَا حَتَّى تَطْهُرَ ثُمَّ تَحِيضَ فَتَطْهُرَ فَإِنْ بَدَا لَهُ أَنْ يُطَلِّقَهَا فَلْيُطَلِّقْهَا طَاهِرًا قَبْلَ أَنْ يَمَسَّهَا فَتِلْكَ الْعِدَّةُ كَمَا أَمَرَهُ اللَّهُ  

A man came to Ibn ʿAbbas while Abu Huraira was sitting with him and said, "Give me your verdict regarding a lady who delivered a baby forty days after the death of her husband." Ibn ʿAbbas said, "This indicates the end of one of the two prescribed periods." I said "For those who are pregnant, their prescribed period is until they deliver their burdens." Abu Huraira said, I agree with my cousin (Abu Salama)." Then Ibn ʿAbbas sent his slave, Kuraib to Um Salama to ask her (regarding this matter). She replied. "The husband of Subai'a al Aslamiya was killed while she was pregnant, and she delivered a baby forty days after his death. Then her hand was asked in marriage and Messenger of Allah ﷺ married her (to somebody). Abu As-Sanabil was one of those who asked for her hand in marriage".  

أَفْتِنِي فِي امْرَأَةٍ وَلَدَتْ بَعْدَ زَوْجِهَا بِأَرْبَعِينَ لَيْلَةً فَقَالَ ابْنُ عَبَّاسٍ آخِرُ الأَجَلَيْنِ قُلْتُ أَنَا {وَأُولاَتُ الأَحْمَالِ أَجَلُهُنَّ أَنْ يَضَعْنَ حَمْلَهُنَّ} قَالَ أَبُو هُرَيْرَةَ أَنَا مَعَ ابْنِ أَخِي يَعْنِي أَبَا سَلَمَةَ فَأَرْسَلَ ابْنُ عَبَّاسٍ غُلاَمَهُ كُرَيْبًا إِلَى أُمِّ سَلَمَةَ يَسْأَلُهَا فَقَالَتْ قُتِلَ زَوْجُ سُبَيْعَةَ الأَسْلَمِيَّةِ وَهْىَ حُبْلَى فَوَضَعَتْ بَعْدَ مَوْتِهِ بِأَرْبَعِينَ لَيْلَةً فَخُطِبَتْ فَأَنْكَحَهَا رَسُولُ اللَّهِ ﷺ وَكَانَ أَبُو السَّنَابِلِ فِيمَنْ خَطَبَهَا  

See hadith 4909  

أَتَجْعَلُونَ عَلَيْهَا التَّغْلِيظَ وَلاَ تَجْعَلُونَ عَلَيْهَا الرُّخْصَةَ لَنَزَلَتْ سُورَةُ النِّسَاءِ الْقُصْرَى بَعْدَ الطُّولَى {وَأُولاَتُ الأَحْمَالِ أَجَلُهُنَّ أَنْ يَضَعْنَ حَمْلَهُنَّ}