Maliks Muwatta Book 21, Hadith Number 8.
Section : Prohibition against Killing Women and Children in Military Expeditions.
Yahya related to me from Malik from Ibn Shihab that a son of Kab ibn Malik (Malik believed that ibn Shihab said it was Abd ar-Rahman ibn Kab) said, “The Messenger of Allah, may Allah bless him and grant him peace, forbade those who fought ibn Abi Huqayq (a treacherous jew from Madina) to kill women and children. He said that one of the men fighting had said, ‘The wife of ibn Abi Huqayq began screaming and I repeatedly raised my sword against her. Then I would remember the prohibition of the Messenger of Allah, may Allah bless him and grant him peace, so I would stop. Had it not been for that, we would have been rid of her.'”