Narrated Abdullah ibn Amr ibn al-‘As (RA): I used to write everything which I heard from the Messenger of Allah (peace be upon him). I intended (by it) to memorise it. The Quraysh prohibited me saying: Do you write everything that you hear from him while the Messenger of Allah (peace be upon him) is a human being: he speaks in anger and pleasure? So I stopped writing, and mentioned it to the Messenger of Allah (peace be upon him). He signalled with his finger to him mouth and said: Write, by Him in Whose hand my soul lies, only right comes out from it.
Sunan Abi Dawud, Book 26, Hadith 6