Imam al-Shafi'i (may Allah have mercy on him) says that some of them said that Yahya bin Sa'id (may Allah have mercy on him) said: The old practice is that the 'aqilah are liable for a third of the blood money or more. We said: The "old practice" may come from one who is followed and whose word is binding, and it may come from governors who are not followed and whose word is not binding. Shall we then abandon the certainty that the Prophet (peace and blessings be upon him) ruled half of one tenth of the blood money upon the 'aqilah because of a conjecture?
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الديات / 16388