Sunan an-Nasa'i, Book 21, Hadith 160 (In-Book) ⓘ
It was narrated that Samurah said: "I offered the funeral prayer with the Messenger of Allah for Umm kab who had died in childbirth, and the Messenger of Allah stood in line at her mid-section to pray."
أَخْبَرَنَا حُمَيْدُ بْنُ مَسْعَدَةَ، عَنْ عَبْدِ الْوَارِثِ، قَالَ حَدَّثَنَا حُسَيْنٌ، عَنِ ابْنِ بُرَيْدَةَ، عَنْ سَمُرَةَ، قَالَ صَلَّيْتُ مَعَ رَسُولِ اللَّهِ صلى الله عليه وسلم عَلَى أُمِّ كَعْبٍ مَاتَتْ فِي نِفَاسِهَا فَقَامَ رَسُولُ اللَّهِ صلى الله عليه وسلم فِي الصَّلاَةِ فِي وَسَطِهَا .
also referenced under: Hadith 1976 (Reference) & Volume 3, Book 21, Hadith 1978 (DarusSalam)