Musnad Ahmad 144:1

Abu Mu'awiyah narrated to us, Al-A'mash narrated to us, from Shaqiq, who said: Mu'awiyah entered upon his maternal uncle, Abu Hashim ibn Utbah, to visit him. He said: So he wept. Mu'awiyah said to him: "What makes you weep, O uncle? Is it a pain that distresses you, or is it greed for the world?" He said: He replied: "Neither of the two. But the Messenger of Allah (peace and blessings of Allah be upon him) made a covenant with us and said: 'O Abu Hashim, perhaps you will attain wealth that is given to some people, yet for you, what suffices of gathering wealth is a servant and a mount in the way of Allah, Blessed and Exalted is He.' And I see that I have gathered."