It is narrated from Sayyidah Umm Sa'd al-Ansariyyah (may Allah be pleased with her), the wife of Zayd bin Thabit (may Allah be pleased with him), that she said: The Messenger of Allah (peace and blessings be upon him) said: "Whoever acquires new wealth, zakah is not due on it until a year has passed over it."
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 21793