The sixth commandment forbids murder. By Stephen Cook’s reckoning in Reading Deuteronomy, chapters 19-21 of Deuteronomy all unpack the meaning of that commandment. They are laws about protecting innocent life.
This works for the laws in ch. 19 about cities of refuge (1-13) and the need for multiple witnesses(15-21) . I am not so sure about the section in the middle about boundary markers. That one seems more about not stealing. So though Deuteronomy does seem to have the Decalogue in mind, the treatment is not in airtight sections.
In regard to the boundary markers, Cook refers to Hosea 5:10 which connects boundary marker fraud to the government of Judah. Micah blames the princes or rulers for land fraud as well. This puts these prophets and Deuteronomy together in hostility toward the monarchy and its disrespect for land tenure.
As chapter 19 was mostly about substituting a kind of due process for swift revenge, chapter 20 tries to temper the lawlessness of war. Cook puts this in the context of the wars of Assyrian imperialism that would have been known in about the time of Josiah. Assyrian warfare threw aside all restraints. It was cruel and unlimited. Warfare for Israel was not to be like that. They had to respect even the trees of the enemy (20:19-20).
Cook says that this chapter is choppy and hard to grasp because it tries to hold two ideas in tension. First, Israel has priority over other nations. God fights for Israel and Israel has a right to take property and women. But there is also a second idea, that of universal humanity (see vs. 10-12 and 19-20). Israel must seek peace and show some restraint.
Cook once again holds that the command to kill them all (v. 13) is symbolic in Deuteronomy, having to do with the elimination of idolatry rather than people.
Verses 5-8, especially reject the idea of the kind of professional army that David had introduced. No mercenary would be exempted from service because he was a newlywed. The recruits contemplated here are farmers and shepherds in a tribal militia. Cook does not deal with the possibility that the law is a carryover from ancient times before David introduced the professional army. He seems to think that Deuteronomy is picturing an ideal Israelite army.
Chapter 21 continues the theme of protecting life and restraint in warfare with a series of laws that extend the laws of chapters 19-20.
I will close this post by summarizing what Cook says about the lex talonis, eye-for-an-eye-tooth-for-a-tooth passage (19:21). Contemporary people often see it as barbaric. Cook counters this with three observations.
First, you don’t have to take it literally. Exodus 21:26-27, which immediately follows the lex talonis in the Covenant Code, does not take it literally.
Second, by requiring exact justice, the law’s intention was to break Hatfield-McCoy like cycles of revenge. You could not keep extracting disproportionate revenge. You had to settle for the eye or the tooth.
Third, it did not impose a fine. So it did not act as though there was some kind of monetary way of getting even. Human life can’t be reduced to monetary value. (Although, see again Exodus 21:26-27).