Musannaf Ibn Abi Shayba 18:780

Abu Bakr narrated to us, he said: Waki’ narrated to us, he said: Sufyan narrated to us, from Rabi’ah ibn Abi Abd al-Rahman, who said: I said to Sa’id ibn al-Musayyib: "How much is [the blood money] for this finger, the little finger, of a woman?" He said: "Ten camels." I said: "And for these two?" meaning the little finger and the one next to it. He said: "Twenty." I said: "And for these three?" He said: "Thirty." I said: "And for these?" and I gestured to the four. He said: "Twenty." I said: "When its injury becomes painful and its affliction becomes great, the compensation for it becomes less?" He said: "Are you an Iraqi?" I said: "A scholar who is verifying, or an ignorant person who is learning." He said: "O son of my brother, it is the Sunnah."