Musannaf Ibn Abi Shayba 35:486

Ali ibn Ishaq narrated to us, from Ibn al-Mubarak, from Ma'mar, who said: Suhayl narrated to me, from his father, from Abu Hurayrah, from the Prophet (peace and blessings of Allah be upon him), who said: "There is no Zakat on what is less than five awsuq." And he mentioned that Abu Hanifah said: "Regarding what is produced from the land, whether it is a little or a lot, there is Zakat."