Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) said: "Whoever has wealth and does not pay its zakah, a bald serpent will be put around his neck as a collar on the Day of Resurrection; it will peck at his head and say: 'I am your wealth that you used to withhold.'" (Concerning this, Allah Almighty said:) "What they withheld will be made a collar around their necks on the Day of Resurrection" [Surah Al Imran: 180].
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 9091