Musnad Ahmad 799:85

Yazid ibn Harun narrated to us, Husayn—meaning al-Mu'allim—informed us, from Abdullah ibn Buraydah, from Samurah ibn Jundab: "The Prophet, may Allah bless him and grant him peace, performed the funeral prayer for the mother of so-and-so, who died during her postpartum period, and he stood at her middle."