If you know right from wrong does it matter who first told you what is right?

If an atheist behaves well does it matter that it is his conscience and not a bible which directs him to do so?

Bx

ETA - what i mean is, if you believe in God you believe the bible is from him, but if you don't believe in god, you believe it is from men, from mankind. So following it makes no sense. Without the faith it doesn't matter. But the faith isn't intrinsic to the behaviour.