It is narrated from Abdullah bin Ubaid bin Nasheet, may Allah have mercy on him, that when Sayyiduna Abu Bakr Siddiq, may Allah be pleased with him, dispatched armies towards Syria, he appointed Yazid bin Abi Sufyan, Amr bin Al-Aas, Shurahbil bin Hasana, and Khalid bin Walid, may Allah be pleased with them, each over separate armies. Yazid bin Abi Sufyan, may Allah be pleased with him, was appointed as the commander over all of them. Sayyiduna Abu Bakr Siddiq, may Allah be pleased with him, himself walked with them on foot, giving them advice. Yazid said: "O Caliph of the Messenger of Allah! Either you ride, or I will get down and walk with you on foot." So Sayyiduna Abu Bakr, may Allah be pleased with him, said: "Neither will I ride, nor will I let you get down. I seek the reward of these steps in the way of Allah." Then he said: "There, many kinds of food and drink will be presented to you. When you eat, mention the name of Allah, and when you finish, say Alhamdulillah. You will meet people who have shaved their heads, their heads will be like straps, split their heads with swords. Some people you will find confined in monasteries, absorbed in worship, leave them to their state." Then he said: "Do not kill any child, woman, or old man. Do not destroy inhabited areas. Do not cut down fruit-bearing trees, or slaughter mute animals, cows, or goats except for food. Do not burn or flood palm groves. Do not commit treachery. Do not show cowardice."