17 “‘You shall not murder.
This one is fairly simple right? Don't murder someone. Some translations use the word "kill", that however would be an inaccurate translation. The word properly means "to murder or kill by negligence." So, killing in self defense, reasonably unavoidable accidental death or warfare are not prohibited by the commandment as the Israelites understood (and we today understand) it. That said, negligence means that doctors, engineers, law enforcement and anyone whose work can be life or death bears an ethical responsibility to make all reasonable assurance that their actions will not cause a life to be lost. It means that parents, teachers and other child care professionals shouldn't neglect those that in their care. Life is precious, and to murder someone or allow death to come to them by simple negligence is sin.
There is more to it than that, however, as Christ expanded our definition of murder:
1 John 3:
15 Everyone who hates his brother is a murderer, and you know that no murderer has eternal life abiding in him.
To hate, in Gods eyes, is the same as murder. Moreover, whoever says that they love God, but hate their brother is a liar. God's standards are higher than people can attain, and that is the reason we need Jesus' saving grace through faith. Many who've never fought are murders in their own heart, and the only way to remove that sin is through repentance and baptism, dying into the death of Christ.