'Unbeliever' in the Bible

But if the unbeliever go away, let them go away; a brother or a sister is not bound in such cases, but God has called us in peace.

But if all prophesy, and some unbeliever or simple person come in, he is convicted of all, he is judged of all;

and what consent of Christ with Beliar, or what part for a believer along with an unbeliever?

But if any one does not provide for his own, and specially for those of his house, he has denied the faith, and is worse than the unbeliever.