From Sahih Bukhari (Hadith 5874):
Narrated Anas:The Prophet (ﷺ) got a ring made for himself and said, "I have got a ring made (for myself) and engraved a certain engraving on it so none of you should get such an engraving on his ring." I saw the glitter of the ring on his little finger
Reference: Bukhari 5874