Musnad Ahmad 937:202

Abu Mu'awiyah narrated to us, Al-A'mash narrated to us, from Al-Ma'rur ibn Suwayd, from Abu Dharr, who said: I arrived at the Prophet, peace and blessings of Allah be upon him, while he was sitting in the shade of the Kaaba. When he saw me approaching, he said: "They are the greatest losers, by the Lord of the Kaaba." I said: "What is the matter with me? Perhaps something has been revealed concerning me. Who are they, may my father and mother be sacrificed for you?" He said: "Those who possess the most wealth, except for the one who says like this," and he scooped [with his hands] in front of him, to his right, and to his left. He said: Then he said: "By the One in Whose hand is my soul, no one among you dies and leaves behind camels, cows, or sheep without paying their Zakat, except that they will come to him on the Day of Resurrection, larger and fatter than they ever were. They will trample him with their hooves and gore him with their horns. Every time the last of them passes, the first of them is brought back to him, until judgment is passed between the people."