Sunan an-Nasa'i, Volume 6, Book 48, Hadith 5213 (DarusSalam) ⓘ

It was narrated that Abu Burdah said: 'Ali said: "The Messenger of Allah [SAW] said to me: 'O 'Ali, ask Allah for guidance and steadfastness,' and he forbade me from placing a ring on this one and this one' - and he pointed to his forefinger and middle finger.

أَخْبَرَنَا مُحَمَّدُ بْنُ مَنْصُورٍ، قَالَ حَدَّثَنَا سُفْيَانُ، عَنْ عَاصِمِ بْنِ كُلَيْبٍ، عَنْ أَبِي بُرْدَةَ، قَالَ قَالَ عَلِيٌّ قَالَ لِي رَسُولُ اللَّهِ صلى الله عليه وسلم ‏ "‏ يَا عَلِيُّ سَلِ اللَّهَ الْهُدَى وَالسَّدَادَ ‏" ‏ ‏.‏ وَنَهَانِي أَنْ أَجْعَلَ الْخَاتَمَ فِي هَذِهِ وَهَذِهِ ‏.‏ وَأَشَارَ يَعْنِي بِالسَّبَّابَةِ وَالْوُسْطَى ‏.‏