Abu Dawud Book 29, Hadith Number 4207.
Chapter : Fashioning a seal in the form of a ring.
Narated By N/A : The tradition mentioned above has also been transmitted by Ibn ‘Umar through a different chain of narrators from the Prophet (PBUH). This version adds: He engraved on it “Muhammad, the Apostle 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