Musnad Ahmad 288:5

Muhammad ibn Ja‘far narrated to us, he said: Shu‘bah narrated to us, from al-Nu‘man, he said: I heard Aws saying: I came to the Messenger of Allah, may Allah bless him and grant him peace, among the delegation of Thaqif. We were in a tent, and those who were in it stood up, except for me and the Messenger of Allah, may Allah bless him and grant him peace. Then a man came and whispered to him, so he said: "Go and kill him." Then he said: "Does he not testify that there is no god but Allah?" He said: "Yes, but he says it as a refuge." He said: "Bring him back." Then he said: "I have been commanded to fight the people until they say: 'There is no god but Allah.' If they say it, their blood and their wealth become forbidden to me, except by its right." I said to Shu‘bah: Is it not in the hadith, then he said: "Does he not testify that there is no god but Allah, and that I am the Messenger of Allah?" Shu‘bah said: I think it is with it, but I do not know.