Musnad Ahmad 27:1500

Husayn narrated to us, Sharik narrated to us, from Muhammad ibn Zayd, from Nafi’, from Ibn Umar, who said: The Messenger of Allah, peace and blessings of Allah be upon him, passed by a woman on the day of the conquest of Makkah who had been killed. He said, "This one was not fighting." Then he forbade the killing of women and children.