Musnad Ahmad 30:3080

Waki’ narrated to us, he said: Zam’ah narrated to us, from al-Zuhri, from Sa’id ibn al-Musayyib, from Abu Hurayrah, he said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Whoever sends forth three of his loins, he shall not enter the Fire except for the fulfillment of the oath."