Sahih Muslim 1485 a
Abu Salama b. 'Abd al-Rahman and Ibn 'Abbas. (Allah be pleased with them) got together in the house of Abu Huraira (Allah be pleased with him) and began to discuss about the woman who gave birth to a child a few nights after the death of her husband. Ibn 'Abbas (Allah be pleased with then) ) said:
Her 'Idda is that period which is longer of the two (between four months and ten days and the birth of the child, whichever is longer). AbuSalama, however said: Her period of 'Idda is over (with the birth of the child), and they were contending with each other over this issue, whereupon Abu Huraira (Allah be pleased with him) said: I subscribe (to the view) held by my nephew (i. e. Abu Salama). They sent Kuraib (the freed slave of Ibn 'Abbas) to Umm Salama to ask her about it. He came (back) to them and informed them that Umm Salama (Allah be pleased with her) said that Subai'ah al-Aslamiyya gave birth to a child after the death of her husband when the few flights (had hardly) passed and she made mention of that to Allah's Messenger (ﷺ) and he commanded her to marry.
حَدَّثَنَا مُحَمَّدُ بْنُ الْمُثَنَّى الْعَنَزِيُّ، حَدَّثَنَا عَبْدُ الْوَهَّابِ، قَالَ سَمِعْتُ يَحْيَى بْنَ سَعِيدٍ، أَخْبَرَنِي سُلَيْمَانُ بْنُ يَسَارٍ، أَنَّ أَبَا سَلَمَةَ بْنَ عَبْدِ الرَّحْمَنِ، وَابْنَ، عَبَّاسٍ اجْتَمَعَا عِنْدَ أَبِي هُرَيْرَةَ وَهُمَا يَذْكُرَانِ الْمَرْأَةَ تُنْفَسُ بَعْدَ وَفَاةِ زَوْجِهَا بِلَيَالٍ ‏.‏ فَقَالَ ابْنُ عَبَّاسٍ عِدَّتُهَا آخِرُ الأَجَلَيْنِ ‏.‏ وَقَالَ أَبُو سَلَمَةَ قَدْ حَلَّتْ ‏.‏ فَجَعَلاَ يَتَنَازَعَانِ ذَلِكَ قَالَ فَقَالَ أَبُو هُرَيْرَةَ أَنَا مَعَ ابْنِ أَخِي - يَعْنِي أَبَا سَلَمَةَ - فَبَعَثُوا كُرَيْبًا - مَوْلَى ابْنِ عَبَّاسٍ - إِلَى أُمِّ سَلَمَةَ يَسْأَلُهَا عَنْ ذَلِكَ فَجَاءَهُمْ فَأَخْبَرَهُمْ أَنَّ أُمَّ سَلَمَةَ قَالَتْ إِنَّ سُبَيْعَةَ الأَسْلَمِيَّةَ نُفِسَتْ بَعْدَ وَفَاةِ زَوْجِهَا بِلَيَالٍ وَإِنَّهَا ذَكَرَتْ ذَلِكَ لِرَسُولِ اللَّهِ صلى الله عليه وسلم فَأَمَرَهَا أَنْ تَتَزَوَّجَ ‏.‏