Sahih al-Bukhari, Volume 9, Book 83, Hadith 33 (USC-MSA) ⓘ
Narrated Ibn `Abbas: The Prophet said, "This and this are the same." He meant the little finger and the thumb.
حَدَّثَنَا آدَمُ، حَدَّثَنَا شُعْبَةُ، عَنْ قَتَادَةَ، عَنْ عِكْرِمَةَ، عَنِ ابْنِ عَبَّاسٍ، عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ " هَذِهِ وَهَذِهِ سَوَاءٌ " ، يَعْنِي الْخِنْصَرَ وَالإِبْهَامَ.
also referenced under: Book 87, Hadith 33 (In-Book) & Hadith 6895 (DarusSalam)