What is sin?

What is a sin? The question came up with the classic question, if you were harboring Jews and the Nazis came to your door, would you lie? We both agreed that lying in this case would be justified, but for different reasons. His justification was that while the person was sinning as the Ten Commandments say thou shall not lie, they would be able to repent in the future. So by sinning, lives would be saved and the person could repent for their sin. I argued that the person did not sin in lying. My justification for this is that while the Ten Commandments do say to not sin, Jesus reminds us of what the goal of the Law was, to love God and to love your neighbor. Jesus broke several commandments, for which he was called out on. He justified himself, in one instance saying "is it better to do good or evil?" Perhaps by not lying I could feel that I had not sinned, but I did evil by allowing innocent lives to be taken. But if I lied, I would be doing good by protecting the innocent lives.

So what if a person was on trial, and I knew that this person was evil, that if they were not in jail that they would harm people, and that they were on trial for something that they were innocent of. Would I be justified in bearing false witness to make sure this evil person did not do harm? I would be saving innocent lives, but I would not be justified.

Micah 6:8 tells us that we are to love justice, give mercy, and walk humbly with God. To lie in this situation would not be loving justice. This does make an assumption that our justice system is just, we will operate under that assumption. To intentionally lie in this case would be against justice. While this person would get what was coming to them, we would not be justified because we went against justice. We should instead stand up for this person who was falsely accused, for then we would be supporting justice. But in doing so, we would have to find a way to protect the innocent lives we know are at risk.

To lie in the first case is justified because the government was unjust. To lie in the second case is not justified because the government is just. I think. We must ensure that we love justice, give mercy, and walk humbly with God for this is what he desires.

So given this, how was Rebekkah justified in telling Jacob to lie to Isaac that he was Esau?