It is narrated from Sayyiduna Ali bin Abi Talib (may Allah be pleased with him), though Zuhayr (may Allah have mercy on him) said: I think he narrated it from the Messenger of Allah (peace and blessings be upon him), that he (peace and blessings be upon him) said: "Bring a quarter of a tenth, that is, one dirham out of every forty dirhams; but nothing (of zakah) is due on you until they reach two hundred dirhams. When they reach two hundred dirhams, five dirhams must be paid from them. And whatever more there is, zakah will be paid at the same rate."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الزكاة / 7521