Musnad Ahmad 2:48

'Affan narrated to us, Hammad bin Salamah narrated to us, from 'Ali bin Zayd, from Abu Rafi': That 'Umar bin al-Khattab was leaning on Ibn 'Abbas, and with him were Ibn 'Umar and Sa'id bin Zayd. He said: "Know that I have not said anything regarding the *kalalah* (the deceased who leaves no direct descendants or ascendants), and I have not appointed a successor after me. And whoever among the captives of the Arabs reaches my death, he is free from the wealth of Allah, the Almighty and Majestic." Sa'id bin Zayd said: "If you had pointed to a man from the Muslims, the people would have trusted you, for Abu Bakr did that and the people trusted him." 'Umar said: "I have seen in my companions an evil greed. I am assigning this matter to these six individuals with whom the Messenger of Allah, peace and blessings of Allah be upon him, died while he was pleased with them." Then 'Umar said: "If one of two men had reached me, and I had then assigned this matter to him, I would have trusted him: Salim, the freed slave of Abu Hudhayfah, and Abu 'Ubaydah bin al-Jarrah."