Musnad Ahmad 30:1540

Hassan narrated to us, Abd al-Rahman ibn Abd Allah ibn Dinar narrated to us, from his father, from Abu Salih, from Abu Hurayrah, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Whoever Allah has given wealth, and he does not pay its Zakat, his wealth will be represented to him on the Day of Resurrection as a bald serpent with two black spots above its eyes. It will seize him by his jawbones on the Day of Resurrection, then it will say: 'I am your wealth, I am your treasure.'" Then he recited this verse: {And let not those who covetously withhold of that which Allah has bestowed on them of His bounty think that it is good for them} [Al-Imran: 180] until the end of the verse.