Sayyiduna Aws bin Aws al-Thaqafi (may Allah be pleased with him) said: I came to the Prophet (peace and blessings be upon him) in the delegation of Thaqif. He said: I was at the lower end of the qiblah side; there was no one there except the Prophet (peace and blessings be upon him), who was sleeping, when a man came to him (peace and blessings be upon him) and whispered something to him. He (peace and blessings be upon him) said: "Go and kill him." Then he said: "Does he not bear witness that there is no deity except Allah (la ilaha illallah), and bear witness that Muhammad is the Messenger of Allah?" He said: Yes, indeed. He (peace and blessings be upon him) said: "I have been commanded to fight the people until they say: la ilaha illallah (there is no deity except Allah). Then when they say it, their blood and their wealth become inviolable for me, except by its right."
Hadith Referenceالمعجم الكبير للطبراني / باب الألف / 588