Sunan Abi Dawud 2999
Tribute, Spoils, and Rulership (Kitab Al-Kharaj, Wal-Fai' Wal-Imarah)
The Special Portion (As-Safi) Of The Prophet (ﷺ) That Was taken From The Spoils Of War
Narrated Yazid ibn Abdullah: We were at Mirbad. A man with dishevelled hair and holding a piece of red skin in his hand came. We said: You appear to be a bedouin. He said: Yes. We said: Give us this piece of skin in your hand. He then gave it to us and we read it. It contained the text: "From Muhammad, Messenger of Allah (ﷺ), to Banu Zuhayr ibn Uqaysh. If you bear witness that there is no god but Allah, and that Muhammad is the Messenger of Allah, offer prayer, pay zakat, pay the fifth from the booty, and the portion of the Prophet (ﷺ) and his special portion (safi), you will be under by the protection of Allah and His Messenger." We then asked: Who wrote this document for you? He replied: The Messenger of Allah (ﷺ).