Musannaf Ibn Abi Shayba 28:575

Waki' narrated to us, he said: Sufyan narrated to us, from Salih, the freed slave of al-Taw'ama, from Abu Hurayrah, who said: The Messenger of Allah (may Allah bless him and grant him peace) said: "I have been commanded to fight the people until they say: 'There is no god but Allah.' So if they say: 'There is no god but Allah,' their blood and their wealth are forbidden to me, except by its right, and their reckoning is with Allah."