'Death' in the Bible

We know that we have passed out of death into life, because we love the brethren. He that loveth not abideth in death.

If any man see his brother sinning a sin not unto death, he shall ask, and God will give him life for them that sin not unto death. There is a sin unto death: not concerning this do I say that he should make request.

All unrighteousness is sin: and there is a sin not unto death.