Sulayman bin Yasar and Irak bin Malik said: A man of Banu Sa'd bin Layth raced a horse, and it trod on the finger of a man of Juhaynah; it kept bleeding and he died. So Umar (may Allah be pleased with him) said to those against whom the claim was made: "Will you swear fifty oaths by Allah that he did not die from it?" They refused and felt uneasy about the oaths. Then he said to the others: "You swear." They too refused, so Umar (may Allah be pleased with him) imposed half the blood money on the Sa'dis.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب القسامة / 16452