God requires attitudes characterized by “charitable thoughts, love, compassion, meekness, gentleness, kindness; peaceable, mild, and courteous speeches and behavior: forbearance, readiness to be reconciled, patient bearing and forgiving of injuries, and requiting good for evil.” Among the sins that the commandment forbids are “sinful anger, hatred, envy, desire of revenge . . . provoking words; oppression, quarreling, striking, wounding, and whatsoever else tends to the destruction of the life of any.”
The Sixth Commandment forbids murder. This commandment is one of God’s moral laws, grounded in His nature, and articulated across the dispensations. The first murderer, Cain, faced God’s judgment for his crime (Gen 4:8–12). After the Flood, God pronounced capital punishment to be the penalty for murder (Gen 9:5–6). Jesus expounded the Sixth Commandment in the Sermon on the Mount (Matt 5:21–26). The apostle John warns church saints against becoming murderers like Cain (1 John 3:12). These and many other scriptures clearly teach that murder is always and everywhere wrong.
The Lord Jesus applied the Sixth Commandment in ways that went beyond physical murder (Matt 5:21–26). According to Jesus, other violations of this commandment include unjustified anger, abusive speech, and character assassination. Jesus was pointing out that the Sixth Commandment (as well as the others) implies more than it states directly. He was also pointing out that God’s people are responsible both to work out and to live out the implications of the commandments.
One attempt at working out the implications of the Ten Commandments can be found in the Westminster Larger Catechism. The catechism devotes an entire section to duties that are required in the Sixth Commandment (Q 135). Another section (Q 136) deals with sins that this commandment forbids.
Remarkably, the catechism does not consider all homicide to be murder. On the contrary, it recognizes the possibility of taking another life lawfully as part of “public justice, lawful war, or necessary defence.” This position is not surprising: the Westminster Standards were drafted by Puritans whose New Model Army trounced the Cavaliers in the English Civil War.