Sunan an-Nasa'i Book 48, Hadith 72
"We heard that the Messenger of Allah forbade filing (the teeth) and tattoos."
He and a companion of his used to stay with Abu Raihanah to learn good things from him. He said: "One day my companion came and told me that he heard Abu Raihanah say: 'The Messenger of Allah forbade filing (the teeth), tattoos, and plucking hairs.'"
"We heard that the Messenger of Allah forbade filing (the teeth) and tattoos."