Musnad Ahmad 28:130

I heard Abdullah ibn Amr saying: The Messenger of Allah, may Allah bless him and grant him peace, came out to us one day like one bidding farewell, and he said: "I am Muhammad, the unlettered Prophet" — he said it three times — "and there is no prophet after me. I have been given the beginnings of speech, its endings, and its comprehensive expressions. I have been taught the number of the keepers of the Fire and the bearers of the Throne. I have been granted intercession, I have been granted safety, and my nation has been granted safety. So listen and obey as long as I am among you; but when I am taken away, then you must adhere to the Book of Allah: declare its lawful as lawful, and declare its unlawful as unlawful."