Muhammad bin Mansur bin Da'ud محمد بن منصور بن داود الطوسي · The Book of Adornment

"We heard that the Messenger of Allah forbade filing (the teeth) and tattoos."

"The Messenger of Allah wanted to write to the Romans, but they (the Companions) said: 'They do not read any letter unless it has a seal.' So he took a ring of silver, and it is as if I can see its whiteness on his hand, and on it were engraved (the words): "Muhammad Rasul Allah (Muhammad the Messenger of Allah)."