(1) Nun. By the pen and what they inscribe. (2) You are not, [O Muhammad], by the favor of your Lord, a madman. (3) And indeed, for you is a reward uninterrupted. (4) And indeed, you are of a great moral character.
I used to write down everything I hear from the Messenger of Allah and I want to memorize. But the Quraysh advised me against it. They said: You write down everything you hear from the Messenger of Allah, and he speaks in contentment and anger. He said: So I stopped, then I mentioned that to the Prophet (PBUH). He pointed with his hand to his mouth and said: Write, for by the One in whose hand is my self, nothing comes out of it except the truth.

404!