Musannaf Ibn Abi Shayba 3:6398

Waki’ narrated to us, he said: Sufyan narrated to us, from Yunus, from al-Hasan, that the delegation of Thaqif came to the Prophet, may Allah bless him and grant him peace, while he was in the mosque in a tent of his. It was said to the Messenger of Allah, may Allah bless him and grant him peace: "O Messenger of Allah, they are polytheists." He said: "Indeed, nothing makes the earth impure."