Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) said: I heard the Messenger of Allah (peace and blessings be upon him) say: "Whoever does not pay the zakah of his wealth, his wealth will be given the form of a speckled serpent on the Day of Resurrection; the owner will flee from it and it will pursue him, until it becomes a collar around his neck." Then the Messenger of Allah (peace and blessings be upon him) recited this verse to us: "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 / 7224