Sayyiduna Abu Hurayrah (may Allah be pleased with him) said that the Messenger of Allah (peace and blessings be upon him) said: "Whoever Allah gives wealth and he does not pay its zakah, his wealth will be made into the likeness of a huge serpent with two black spots (over its eyes), and it will become a collar around his neck. Then it will seize him by his jaws and say: 'I am your wealth, I am your treasure.'" Then he (peace and blessings be upon him) recited this verse: "Let not those who are miserly with what Allah has given them of His bounty think that it is better for them; rather, it is evil for them. Soon, on the Day of Resurrection, they will be collared with what they were miserly with." [Surah Al Imran: 180]
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الزكاة / 7223