Sulayman bin Yasar said that a man from Banu Sa'd raced a horse, and it trampled the finger of a man from Juhaynah, and he died because of it. Umar (may Allah be pleased with him) said: Will you swear that he did not die from it? They refused and felt reluctant to take the oaths. He said it to the others, and they too felt reluctant to take the oath.
(b) Imam al-Shafi'i (may Allah have mercy on him) said: The Messenger of Allah (peace and blessings be upon him) placed the oath upon the Ansaris because they would thereby become entitled. When they did not accept the oath, the Prophet (peace and blessings be upon him) turned the oath back onto the Jews. Umar (may Allah be pleased with him) placed the oath upon Banu Layth, then, upon their refusal, took the oath from the Juhanis. This is the practice of our muftis.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الشهادات / 20738