Musnad Ahmad 30:1313

Uthman ibn Umar Abu Muhammad narrated to us, he said: Ibn Abi Dhi'b narrated to us, from Sa'id al-Maqburi, from Abu Hurairah, that the Messenger of Allah, may Allah bless him and grant him peace, said: "The Hour will not be established until my Ummah takes the path of the nations before it, span by span and cubit by cubit." A man said: "O Messenger of Allah, like Persia and Rome?" He said: "And who are the people if not them?"