Musannaf Ibn Abi Shayba 5:59

Ali bin Hashim narrated to us, from Ibn Abi Layla, from Abd al-Karim, from Amr bin Shu'ayb, from his father, from his grandfather, from the Prophet, peace and blessings be upon him, who said: "There is nothing [due as Zakat] in less than two hundred dirhams."