Sunan an-Nasa'i, Hadith 1979 ⓘ
It was narrated from Samurah bin Jundab: That the Messenger of Allah offered the funeral prayer for a mother who had died in childbirth, and he stood in line with her middle.
أَخْبَرَنَا عَلِيُّ بْنُ حُجْرٍ، قَالَ أَنْبَأَنَا ابْنُ الْمُبَارَكِ، وَالْفَضْلُ بْنُ مُوسَى، ح وَأَخْبَرَنَا سُوَيْدٌ، قَالَ أَنْبَأَنَا عَبْدُ اللَّهِ، عَنْ حُسَيْنٍ الْمُكْتِبِ، عَنْ عَبْدِ اللَّهِ بْنِ بُرَيْدَةَ، عَنْ سَمُرَةَ بْنِ جُنْدُبٍ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم صَلَّى عَلَى أُمِّ فُلاَنٍ مَاتَتْ فِي نِفَاسِهَا فَقَامَ فِي وَسَطِهَا .
also referenced under: Book 21, Hadith 163 (In-Book) & Volume 3, Book 21, Hadith 1981 (DarusSalam)