(52) باب النَّهْىِ عَنِ الْخَاتَمِ، فِي السَّبَّابَةِ
It was narrated that 'Ali said:
"The Messenger of Allah [SAW] 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.
Reference: Sunan an-Nasa'i 5211
In-book reference: Book 48, Hadith 172
English translation: Vol. 6, Book 48, Hadith 5214