Musnad Ahmad

Yazid ibn Harun narrated to us, Nafi‘ ibn ‘Umar narrated to us, from Umayyah ibn Safwan, from Abu Bakr ibn Abi Zuhayr, from his father, who said: I heard the Messenger of Allah, peace and blessings be upon him, say in his sermon at al-Nabawah or al-Banawah near al-Ta’if: "Soon you will know the people of Paradise from the people of the Fire," or, "the best of you from the worst of you." And I do not know except that he said: the people of Paradise from the people of the Fire. So a man from among the Muslims said: "By what, O Messenger of Allah?" He said: "By good praise and bad praise; you are witnesses over one another."