Ayoub al-Sakhtiyani أيوب السختياني · The Book on Zakat

"Whoever acquired wealth, then there is no Zakat on it until the Hawl has passed while it is in his possession."

"The Messenger of Allah made Sadaqatul-Fitr an obligation upon the male and female, the free and the bondsmen, as a Sa of dried dates or a Sa of barley." He said: "So the people equated that to half a Sa of wheat."