From the Prophet ﷺ, who said, "This and this are equal," meaning the little finger and the thumb.
عن النبي ﷺ قال: هذه وهذه سواء، يعني الخنصر والإبهام.
Bukhari narrated it in the chapter on blood-money (6895) from Adam, who said, Shuba narrated to us, from Qatada, from Ikrima, from Ibn Abbas, and he mentioned it.Abu Dawud (4559) and Ibn Jarud (783) both narrated it through the hadith of Abdul-Samad bin Abdul-Warith, who said, Shuba narrated to me with his chain, and it contains, "The fingers are equal, and the teeth are equal, the incisor and the molar are equal, this and this are equal."Abu Dawud said, "Nadr bin Shumayl also narrated it, from Shuba, with the same meaning as Abdul-Samad."