Muwatta Malik, Book 43, Hadith 1567 (In-Book)

Yahya related to me from Malik from Ibn Shihab that Said ibn al- Musayyab used to say, "The full blood-money is payable for cutting off both lips, but when the lower one only is cut off, two-thirds of the blood-money is due for it."

حَدَّثَنِي يَحْيَى، عَنْ مَالِكٍ، عَنِ ابْنِ شِهَابٍ، عَنْ سَعِيدِ بْنِ الْمُسَيَّبِ، أَنَّهُ كَانَ يَقُولُ فِي الشَّفَتَيْنِ الدِّيَةُ كَامِلَةً فَإِذَا قُطِعَتِ السُّفْلَى فَفِيهَا ثُلُثَا الدِّيَةِ ‏.‏

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also referenced under: Book 43, Hadith 6 (USC-MSA)