Bushayr bin Yasar narrates from Sayyiduna Sahl bin Abi Hathmah (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) began the oath with the two Ansaris, but when they did not take the oath, he (peace and blessings be upon him) turned the oaths back onto the Jews.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الشهادات / 20733