Musnad Ahmad 30:2710

Hajjaj and Yazid narrated to us, they said: Ibn Abi Dhi'b informed us, from Sa'id al-Maqburi, from Abu Hurairah, from the Prophet, peace and blessings of Allah be upon him, who said: "A time will surely come upon the people when a person will not care about what he takes of wealth, whether it is from a lawful source or an unlawful one."