"I heard Aws say: 'I came to the Messenger of Allah said: Leave him alone. Then he said: I have been commanded to fight the people until they say La ilaha illallah. If they say it, then their blood and their wealth become forbidden to me, except for a right that is due. (One of the narrators) Muhammad said: I said to Shu'bah: 'Doesn't the Hadith contain: Does he not testify to La ilaha illallah (there is none worthy of worship except Allah) and that I am the Messenger of Allah?' He said: 'I think it is both, but I do not know.'"
Sunan an-Nasa'i Book 37, Hadith 17