Musnad Ahmad 33:686

Surayj ibn al-Nu'man narrated to us, Abdullah ibn Wahb narrated to us, from Amr ibn al-Harith, that Abu al-Zubayr narrated to him, that he heard Jabir ibn Abdullah mentioning that the Messenger of Allah, peace and blessings of Allah be upon him, said: "Regarding what is watered by rivers and rain, there is a tenth (ushr). And regarding what is watered by the camel-drawn bucket (saniyah), there is half a tenth."