Musnad Abu Ya'la al-Mawsili 155:178

Abu Yusuf al-Jizi narrated to us, Mu'ammal ibn Isma'il narrated to us, Sufyan al-Thawri narrated to us, Muhammad ibn 'Amr narrated to us, from Abu Salamah, from Abu Hurayrah, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "The poor of the Muslims will enter Paradise before their rich by five hundred years."