Musnad Ahmad 1153:2342

Ya'qub narrated to us, he said: My father narrated to us, from Ibn Ishaq, he said: Yazid ibn Ruman narrated to me, from 'Urwah, from 'Aishah, she said: The Messenger of Allah, peace and blessings of Allah be upon him, commanded that the slain be cast into the pit (al-qalib), and they were cast into it, except for Umayyah ibn Khalaf, for he had swollen inside his armor and filled it. So they went to move him, and he fell apart, so they left him and cast upon him what covered him of dirt and stones. When he had cast them into the pit, the Messenger of Allah, peace and blessings of Allah be upon him, stood over them and said: "O people of the pit, have you found what your Lord promised you to be true? For I have found what my Lord promised me to be true." She said: His companions said to him: "O Messenger of Allah, do you speak to a people who are dead?" He said to them: "They have indeed come to know that what I promised them is true." 'Aishah said: And the people say: "They have indeed heard what I said to them," but the Messenger of Allah, peace and blessings of Allah be upon him, only said: "They have indeed come to know."