Amr bin Hisham عمرو بن هشام · The Book of Fighting [The Prohibition of Bloodshed]

"We were with the Messenger of Allah said: 'Do not kill him, for I have been commanded to fight the people until they say La ilaha illallah, and if they say it, their blood and their wealth are safe from me, except for a right that is due, and their reckoning will be with Allah.'"