Musnad Ahmad 799:136

'Abd al-Samad narrated to us, my father narrated to us, Husayn narrated to us, Ibn Buraydah narrated to us, that he heard Samurah ibn Jundub saying: "What prevents me from speaking about much of what I used to hear from the Messenger of Allah (may Allah bless him and grant him peace) is that there are those here who are older than me, and I was a young boy at that time. Yet, I used to memorize what I heard from him: 'I prayed behind the Messenger of Allah (may Allah bless him and grant him peace), and he prayed over Umm Ka'b, who died while she was in her postpartum period. The Messenger of Allah (may Allah bless him and grant him peace) stood for the prayer over her at her middle.'"