Chapter 36: Signet-Rings (Kitab Al-Khatam)
The tradition mentioned above has also been transmitted by Ibn 'Umar through a different chain of narrators from the Prophet (ﷺ). This version adds: He engraved on it "Muhammad, the Messenger of Allah." and said: "No one must engrave anything in the manner of this signet-ring of mine. He then transmitted the rest of the tradition.
Sunan Abi Dawud 4219