Sunan an-Nasa'i, Volume 4, Book 27, Hadith 3536 (DarusSalam)

It was narrated from Al-Miswar bin Makhramah that Subai'ah Al-Aslamiyyah gave birth one day after her husband died. She came to the Messenger of Allah and asked his permission to marry, and he gave her permission to marry and she married.

أَخْبَرَنَا مُحَمَّدُ بْنُ سَلَمَةَ، وَالْحَارِثُ بْنُ مِسْكِينٍ، قِرَاءَةً عَلَيْهِ وَأَنَا أَسْمَعُ، - وَاللَّفْظُ لِمُحَمَّدٍ - قَالاَ أَنْبَأَنَا ابْنُ الْقَاسِمِ، عَنْ مَالِكٍ، عَنْ هِشَامِ بْنِ عُرْوَةَ، عَنْ أَبِيهِ، عَنِ الْمِسْوَرِ بْنِ مَخْرَمَةَ، أَنَّ سُبَيْعَةَ الأَسْلَمِيَّةَ، نُفِسَتْ بَعْدَ وَفَاةِ زَوْجِهَا بِلَيَالٍ فَجَاءَتْ رَسُولَ اللَّهِ صلى الله عليه وسلم فَاسْتَأْذَنَتْ أَنْ تَنْكِحَ فَأَذِنَ لَهَا فَنَكَحَتْ ‏.‏

sunnah.com