What does the word “murder” mean? Some would limit its definition to that which is “illegal” killing. This is a huge mistake… it would mean that Hitler, Stalin, Mao, and other tyrants of history are actually not murderers. Furthermore, it would exclude the killing of the unborn. Needless to say, if “murder” were to be limited to illegal killing, it would make no sense as an ethical command.
Still others define murder as being any killing, without exception. These people, if they were to be consistent, would also oppose all killing without exception. Yet this too is a mistake. Genesis 9:6, for example, allows for the killing of those who commit murder. So if all killing were murder, than not all murder would be wrong, which would contradict Exodus 20:13 (Thou shall not murder.) furthermore, the numerous cases where God commands the Israelites to kill specific people would have been wrong as well.
First off, its important to realize that God is the owner of human life. So, God has the right to dispose of it when he sees fit. This may seem harsh to us, but keep in mind that in God’s eyes, we all deserve eternal punishment. So for God to tell one man to kill another man (As he often does in the Old Testament) is giving the man being killed no worse than he deserves.
That said, the Bible does not specifically define “murder” at any point. The Bible generally does not define its commands. With that being said, its still fairly easy to tell that killing a person who is trying to kill you, or who is trying to kill someone else, is not murder. Genesis 9:6 pretty clearly shows us that. If it is acceptable to kill someone after they have committed murder, than it is acceptable to kill them to save the person’s life who they are trying to kill. It is not much of a logical leap to take this assumption. Furthermore, Exodus 22:2 permits the killing of a thief when he breaks in at night. The owner would not be aware of the thief’s intentions or easily able to prevent the thief from committing his crime without killing him (Because he would not know that he was merely a thief, rather than a murderer.)
That said, what about utilitarian calculations? Say, killing one innocent (defined above) person to save five? Bombing one city to force another country to surrender? Are these things acceptable? No. Why? Because these actions do not limit their damage to the people who actually commit the evil actions. Would it be OK to kill one person on the street to save three people who need organs? Of course not. Would it be OK to kill children in a “hostile” nation one by one until the enemy nation surrendered? Of course not. The human conscience knows that these actions are murder, while self-defense is not. But many will deny that fact when it comes to the military. They are hypocritical.
I’ve recommended it before, but this is an excellent article on the subject: