The Hebrew of the sixth commandment is about as terse as it can be. It consists of two words that are the Hebrew equivalent of "No killing." However, enough other scriptures appear in God's Word to let us know that the commandment means that God does not permit violent and premeditated killing of one perceived as an enemy. Exodus 21:12-14 clarifies this:
He who strikes a man so that he dies shall surely be put to death. However, if he did not lie in wait, but God delivered him into his hand, then I will appoint for you a place where he may flee. But if a man acts with premeditation against his neighbor, to kill him by treachery, you shall take him from My altar, that he may die.
This clearly separates a premeditated murder from an accidental killing. One can discern from verse 14 that, under this circumstance, constituted civil authorities are permitted by God to enact the death penalty.
Verses 12 and 13 imply that no amount of money or property settlement can atone for the destruction of the image of God in a murdered person. Even if the death was truly accidental, the killer still had to flee to a city of refuge. But for one guilty of deliberate murder, there were no sanctuaries whatsoever to flee to, not even the altar of God.
John W. Ritenbaugh
The Sixth Commandment