Briefly stated this means that we should fear and love God that we
may not hurt or harm our neighbor in his body, but help and befriend him
in every bodily need.
The preceding commandments deal with divine and paternal authority. Now we learn how we should live with one another. While this commandment forbids individuals to kill except in self-defense, it does not forbid God to kill. Likewise, it does not forbid capital punishment, for God has assigned to government a different role than that assigned to individuals. God instituted government as an instrument of His wrath. The role of government is that of divine avenger, and the authority that God has given to government rests upon the authority given to parents. Men have a responsibility to defend themselves and their families. Under certain circumstances, the Law of Moses required parents to bring their own children to judgment and sentence them to death. This authority is delegated to rulers who are to use it to condemn and punish evildoers, while encouraging those who do what is right. Therefore, this commandment forbids murder.
While the government only requires outward obedience to this commandment,
Christ made it clear that spiritually this commandment condemns those who
harbor hatred or anger in their hearts as well as those who try to hurt
their neighbor in any way, even with hateful words or gestures. (Matthew
5:21) While it is proper for parents and government to express anger in
their role as God's representatives, this commandment condemns unrighteous
anger. We are not to be angry with our neighbor without cause.
God, knowing that the world is evil and that this life has much unhappiness, instituted this commandment, as well as the others, to protect us from evil. However, these commandments are often broken, and we must live among those who would do us harm, in which case we would have just cause to be hostile to them. Therefore, it is no contradiction that God forbids murder but allows weapons and arms. On the contrary, to prevent murder God's commands us to have weapons and arms. (Luke 22:36)
In this world envy is far too common. A neighbor who envies the fact that you have a nicer house, a larger family, or greater possessions than he, may be sulky or speak ill of you behind your back.
Thus by the devil's incitement, you may have enemies who cannot bear to see you have any good, either bodily or spiritual. When we know of such people, our hearts may rage and long to take vengeance. Then comes cursing and blows, from which follow misery and possibly murder. Here God, like a kind father, is one step ahead of us, making it clear that He wants us to settle the quarrel before any misfortune comes of it. Therefore, by this commandment God endeavors to keep the peace and protect us against the crimes and violence of others, while protecting our neighbor so that we do him no harm.
This commandment not only forbids murder, but also forbids all evil thoughts, emotions, words, and plotting that would lead to murder. For if the deed is evil, the desire to commit it is likewise evil. Therefore, we are not to be rude and hateful to those who have done us wrong, even if they fully deserve it. If a crime has been committed, let the courts handle it. God does not want us to harbor bitterness against our neighbor. Instead, we are to keep this commandment before our eyes, using it as a mirror to show us our sin and bring our heart into line while asking God for help to put evil thoughts out of our mind. Do not let the sin of others lead you to sin. Instead learn to calm your wrath, and have a patient, gentle heart; especially toward those who give you cause to be angry, namely, your enemies.
To put it simply, we should not harm anyone, nor should we instigate trouble or try to get others to harm him. We are not to plot evil or to assent to any means by which others might bring harm to someone. Our heart should not be ill disposed toward anyone, nor should we harbor anger and hatred or wish him ill. This applies especially to those who wish you evil or inflict evil upon you. It goes without saying that we are not to do evil to those who do us good, for to do evil to those who do you good is totally Satanic.
While this commandment clearly condemns those who actively harm their neighbor, it also condemns those who bring harm to their neighbor by refusing to help him in his time of need. (If you refuse to help him when he is freezing you cause him to freeze to death. If you refuse to help him when he is starving you cause him to starve to death.) The same holds true if he is sentenced to death and you know he is innocent but say nothing. If you could have helped him, but do nothing, you have killed him. The fact that you did not actively do him harm is meaningless, you withheld your love from him and deprived him of the benefit whereby his life would have been saved.
When I speak of helping those in need I am not talking about
the false philanthropy of rulers, who would appear as benefactors at someone
else's expense, but rather of personal one on one compassion. (Luke 22:25-26)
The Word of God condemns those who refuse to help those who are in distress
or danger. On the last day Christ will say to such people, "I was hungry
and you gave Me no food; I was thirsty, and you gave Me nothing to drink;
I was a stranger, and you refused to take Me in; naked, and you clothed
Me not; sick and in prison and you did not visit Me". (Matt.25, 42) In
short, you would have allowed Me (and Mine) to be killed by wild beasts;
to die of hunger, thirst, and cold; or to rot in prison without help. For
although you have not actively done this, you have nevertheless helped
to that end.
Even unsaved people realize that it is wrong to refuse to help when we are able to do so. If someone is drowning or has fallen into a pit and I am able to pull them out but do nothing, the world would rightly regard me as a murderer and a criminal.
While even the heathen do good to their friends, God has called us to a higher standard. He does not want us to cause harm, or allow harm to come, to any man. Instead we are to love our enemies, bless those who curse us, do good to those who hate us, and pray for those who exploit us and persecute us. (Matt. 5:44-46)
Through this commandment God directs and urges us to true righteousness by leading us to show gentleness, patience, love, and kindness even to our enemies. He would also have us remember at all times that He is our God, that He will help, assist, protect, and strengthen us that we might overcome, and put out of our mind, any desire of revenge.
If we would practice and teach what the Bible says in regard to this commandment, we would have more good works to do than we could handle. However, the monks care nothing for such works since such works detract from their unscriptural brand of piety. They might even condemn such works as a hindrance to piety, for such works would require them to leave their cloister and go out into the world. Why if everyone practiced Biblical righteousness the monks would be no different than ordinary Christians, and everyone would see how they presently delude the world with a false, hypocritical show of holiness. They treat God's commandments as if they were not real commandments, but mere counsels, and toss them to the wind as if they were unnecessary. At the same time, they shamelessly boast of their unscriptural piety as the most perfect life, in order that they might lead a pleasant, easy life. They seclude themselves in cloisters, so that they might not experience wrong from any one or show kindness to anyone. However, the commandments of God provide the only true standard of righteousness and the only truly good works. In comparison, obedience to all of the commandments of men is but stench and filth in the eyes of God. All of the methods men have devised for attaining holiness deserve only His wrath and damnation.
[The above is based upon, and closely follows, Martin Luther's explanation of the fifth commandment.]