Commands to an Army

With Arabia settled, Abu Bakr turned to the two empires on its borders, Persia and Byzantium. He sent Khalid ibn al-Walid into Iraq, and then armies toward Syria under Yazid ibn Abi Sufyan, Shurahbil ibn Hasanah, 'Amr ibn al-'As and Abu 'Ubaydah ibn al-Jarrah. When the Byzantines massed against them, he ordered Khalid to cross from Iraq to Syria, which he did by a hard desert march.

He walked out with Yazid ibn Abi Sufyan to see him off, and gave him instructions that Malik preserved in al-Muwatta': do not kill women, children or the elderly; do not cut down fruit-bearing trees; do not destroy inhabited places; do not slaughter sheep or camels except for food; do not burn or drown palm trees; do not take from the spoils dishonestly; and do not be cowardly. You will find people who have shut themselves away in worship — leave them to what they have devoted themselves to.

Sunni scholars explain the purpose of these campaigns as carrying the message beyond Arabia and removing the powers that stood between people and hearing it — not forcing anyone's conscience, for ﴿لَا إِكْرَاهَ فِي الدِّينِ﴾ (“there is no compulsion in religion”) (2:256), and peoples who came under Muslim rule kept their faiths under protection. The Prophet ﷺ himself had forbidden the killing of women and children in war (Sahih al-Bukhari 3015). Abu Bakr lived to hear of early victories, but the great battles would be fought under 'Umar.