Musnad Ahmad 27:185

'Abbad ibn al-'Awwam narrated to us, Sufyan ibn Husayn narrated to us, from al-Zuhri, from Salim, from Ibn 'Umar, that the Messenger of Allah (peace and blessings of Allah be upon him) wrote the document of Zakat (charity), but he did not bring it out to his workers until he passed away, so he attached it to his sword. When he passed away, Abu Bakr acted upon it until he passed away, then 'Umar until he passed away. It contained: "For five camels, one sheep; for ten, two sheep; for fifteen, three sheep; for twenty, four sheep; and for twenty-five, a bint makhad (a one-year-old female camel)." 'Abdullah ibn Ahmad said: My father said: "Then an illness afflicted me in the gathering of 'Abbad ibn al-'Awwam, so I wrote the remainder of the hadith, but I think I did not understand some of it, so I doubted the rest of the hadith and left it."