Heidelberg Catechism – Lord’s Day 40
Q. What does God require in the sixth commandment?
A. That I am not to abuse, hate, injure, or kill my neighbor, either with thought, or by word or gesture, much less by deed, whether by myself or through another, but to lay aside all desire for revenge; and that I do not harm myself or willfully expose myself to danger. This is why the authorities are armed with the means to prevent murder.
Q. But does this commandment speak only of killing?
A. In forbidding murder God means to teach us that he abhors the root of murder, which is envy, hatred, anger, and desire for revenge, and that he regards all these as hidden murder.
Q. Is it enough, then, if we do not kill our neighbor in any of these ways?
A. No; for when God condemns envy, hatred, and anger, he requires us to love our neighbor as ourselves, to show patience, peace, gentleness, mercy, and friendliness toward him, to prevent injury to him as much as we can, also to do good to our enemies.