Musnad Ahmad 27:298

'Attab ibn Ziyad narrated to us, Abdullah—meaning Ibn al-Mubarak—informed us, Malik ibn Anas informed us, from Nafi', from Ibn 'Umar: "That the Prophet, peace and blessings of Allah be upon him, saw a slain woman in one of his military expeditions. He disapproved of that and forbade the killing of women and children."