During his life, Muhammad gave various injunctions to his forces and adopted practices toward the conduct of war. The most important of these were summarized by Muhammad’s companion and first Caliph, Abu Bakr, in the form of ten rules for the Muslim army:
O people! I charge you with ten rules; learn them well!
Stop, O people, that I may give you ten rules for your guidance in the battlefield. Do not commit treachery or deviate from the right path. You must not mutilate dead bodies. Neither kill a child, nor a woman, nor an aged man. Bring no harm to the trees, nor burn them with fire, especially those which are fruitful. Slay not any of the enemy’s flock, save for your food. You are likely to pass by people who have devoted their lives to monastic services; leave them alone.
Aboul-Enein, H. Yousuf and Zuhur, Sherifa, Islamic Rulings on Warfare, p. 22, Strategic Studies Institute, US Army War College, Diane Publishing Co., Darby PA, ISBN 1-4289-1039-5