Ibn al-Musayyib (may Allah have mercy on him) said: Sayyiduna Umar (may Allah be pleased with him) ruled regarding the fingers: for the thumb 13 camels, for the one next to it 12, for the middle finger 10, for the one next to it 9, and for the little finger 6.
This continued until the letter of the Prophet (peace and blessings be upon him) was found with the family of Amr bin Hazm (may Allah be pleased with him), in which "10 camels for every finger" was mentioned. Sa'id (may Allah have mercy on him) said: Then the ruling was made according to that letter.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الديات / 16286