Write down; for by the One in Whose Hand my soul is, nothing comes out of it except the truth

‘Abdullāh ibn ‘Amr (may Allah be pleased with him) reported: I used to write down everything I heard from the Messenger of Allah (may Allah's peace and blessings be upon him) in order to memorize it by writing, but men from the Quraysh forbade me from doing so, saying: The Messenger of Allah (may Allah's peace and blessings be upon him) is a human being who speaks in pleasure and anger and so he is likely to err. Therefore, I stopped writing.

I told the Prophet (may Allah's peace and blessings be upon him) about what they said, and he pointed with his finger to his mouth and said: Write down, for the One in Whose Hand my soul is, nothing comes out of it except the truth, in all conditions and in pleasure and anger. And Allah Almighty says about His Prophet (may Allah's peace and blessings be upon him): {Nor does he speak out of his own desire*. It is but a revelation sent down [to him].} [Surat an-Najm: 3-4]