(44, 45) باب عَقْلِ الأَصَابِعِ
It was narrated from Ibn 'Abbas that the Propher said:
"this and this are the same,": meaning the little finger and the thumb. (ID)
Reference (ID): Sunan an-Nasa'i 4847 (ID)
In-book reference (ID): Book 45, Hadith 142 (ID)
English translation (ID): Vol. 5, Book 45, Hadith 4851 (ID)