Muhammad bin al-Hasan (may Allah have mercy on him) says: Abu Hanifah narrated that to us from al-Haytham, from al-Sha'bi, from Sayyiduna Umar (may Allah be pleased with him). And the people of Madinah say that Sayyiduna Umar (may Allah be pleased with him) fixed the blood money for the people of silver at 12000 dirhams. Muhammad says: The people of Madinah have spoken the truth about Sayyiduna Umar (may Allah be pleased with him), that he fixed the blood money at 12000 dirhams; but he fixed it at twelve thousand dirhams by the weight of six.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الديات / 16187