Mishkat al-Masabih 16 Retaliation كتاب القصاص 35

عَنِ ابْنِ عَبَّاسٍ عَنِ النَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ قَالَ: «هَذِهِ وَهَذِهِ سَوَاءٌ» يَعْنِي الخِنصرُ والإبهامَ. رَوَاهُ البُخَارِيّ

Ibn ‘Abbas reported the Prophet as saying, “This and that are equal,” meaning the little finger and the thumb. Bukhari transmitted it.