Because it is against the law to commit murder, and because it isn't your life to take, only God can take someones life.

No one has the right to take it upon themselves to take another person's life. Only God can create life, so all life belongs to Him. Therefore, only God has the right to take life.

Read The Ten Commandments, one of which is "Thou Shalt Not Kill". The life of a person is precious in so many ways, and to take that life destroys, and forever changes the lives, of all who loved that person. It is also against the law to take another person's life.

Another view:

I think we need to make a clarification between murder, killing and justifiable homicide.

Justifiable homicide means someone is forced into a decision to either protect the life of another or let that life be taken, but in protecting someone there may be a life to be taken--that of the intended perpetrator. Self-defense is a decision to protect ones self from harm, it is not a premeditated desire to take anothers life. I do believe meditation and motivation are critical components.

Also, killing is, to many, not murder while others do believe taking a life for any reason is considered against the Commandments. So, some ask, why would God then command certain situations under which such killing was in compliance with Scripture?

In rudimentary civilization, in the exodus from Egypt and throughout Biblical times, there were no jails, no prisons. There were limited ways to punish someone. They could not suddenly invent jails, then in the middle of the desert find the needed iron to build this new creation. If they left someone behind in the desert, they would surely die an even longer, slower, more painfully punishing death. Killing in combat was seen as a fight of good vs evil, of those who did not believe in God versus those who did, of those intent upon committing evil/harm to Believers vs. stopping this in combat.

Over the years, through various Holocausts, crusades et al, this has been used as a false rationale to commit what in essence was mass murder. But, that battle between the forces of good vs the forces of evil has been waged since the first battle of believing the serpent or believing the Creator.

Murder is a premeditated action, or the result of a premeditated act of evil with intention to harm another, not to protect ones own life. It is stealing that life, it is acting in such a way that we are taking something which can never be put back in its place and doing so with the express knowledge what we are doing is permanent.

Another view:

Murder is morally wrong because all human beings are equal - and have the right to life. Taking a life is taking away that right (this is why euthanasia is regarded by many as being in a grey area).

We don't want to be murdered so we create within our society laws that prevent the said action.

Although pragmatic humanists believe that murder is right if it results in more happiness than suffering - a common analogy used is that - it is right to kill Hitler and prevent the 2nd World War

Another view:

In response to the above, those examples cited were taken from the Old Testament of The Bible, and Christians are no longer expected to live by those laws, but by the New Testament instead. After the death of Jesus, God gave us the New Testament to live by, so those examples cited no longer apply to Christians.

Also, the question asked if "murder" is wrong, not capitol punishment or killing someone in self defense. There is a huge difference between the two.

And lastly, the example of it being "right to kill Hitler and prevent the 2nd World War" is simply not a fair example. To execute a murderer, as Hitler was, would have been perfectly acceptable and preferred by Christian and non Christian standards.

Another view:

Every person is born with the right to live their life free from the interference of any other person. That right springs forth from the concept of natural rights or human rights. Murder is the killing of another human unlawfully. No person has the right to take the life of another person by the act of murder. Unfortunately for some, we must depend on governments to protect our natural rights and this is not possible in some areas of the world.