"The Messenger of Allah said to me: 'Say: O Allah, guide me and make me steadfast,' and he forbade me to put a ring on this one and this one" - and Bishr (one of the narrators) pointed to his forefinger and middle finger. And 'Asim said: "One of the two of them."
Sunan an-Nasa'i Book 48, Hadith 173
← Previous Hadith "The Messenger of Allah forbade me to wear a ring on this one and this one," meaning the forefinger and middle finger. And this is the wording of Ibn Al-Muthanna.

Sunan an-Nasa'i Book 48, Hadith 172 Next Hadith → When entering the Khala', the Messenger of Allah would take off his ring.

Sunan an-Nasa'i Book 48, Hadith 174