Bahz bin Hakim narrates from his father, from his grandfather (may Allah be pleased with him), who said: I heard the Messenger of Allah (peace and blessings be upon him) say: "If a man's slave comes to him and asks him for something surplus that he has, and he withholds it from him, then on the Day of Resurrection it will be summoned to him in the form of a huge serpent, and it will cling to the very thing he withheld."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الزكاة / 7764