Thou shalt not kill. Here again is a moral precept included in all codes, and placed by all in a prominent position. Our first duty towards our neighbour is to respect his life. When Cain slew Abel, he could scarcely have known what he was doing; yet a terrible punishment was awarded him for his transgression (Genesis 4:11-14).
After the flood, the solemn declaration was made, which thenceforward became a universal law among mankind—"Whoso sheddeth man's blood, by man shall his blood be shed: for in the image of God made he man" (Genesis 9:6).
In the world that followed the flood, all races of men had the tradition that only blood could expiate blood. In the few places where there was an organised government, and a systematic administration of justice, the State acted on the principle, and punished the murderer capitally.
Elsewhere, among tribes and races which had not vet coalesced into states, the law of blood-revenge obtained, and the inquisition for blood became a private affair. The next of kin was the recognised" avenger," upon whom it devolved to hunt out the murderer and punish him.
Here the sin is simply and emphatically denounced, the brevity of the precept increasing its force. The Israelites are told that to take life is a crime. God forbids it. As usual, no exceptions are made.
Exceptions appear later on (Numbers 35:22-25; Deuteronomy 4:42; etc.); but the first thing is to establish the principle. Human life is sacred. Man is not to shed the blood of his fellow-man. If he does, of his hand will the life taken surely be required.
The casuistic question whether suicide is forbidden under this precept, probably did not occur to the legislator or to the Hebrews of his time. Neither the Hebrews, nor the Egyptians, among whom they had so long lived, were addicted to suicide; and it is a general rule that laws are not made excepting against tolerably well-known crimes.
It has been argued that angry thoughts and insulting words were forbidden by it on the strength of our Lord's comment in the Sermon on the Mount (Matthew 5:21, Matthew 5:22). But it seems to the present writer that in Matthew 5:21-47 our Lord is not so much explaining the Jewish law as amplifying it on his own authority—note the repetition of the phrase, "But I say unto you"—and making it mean to Christians what it had not meant to Jews.