The Anchor Bible simply says this was probably “a late addition to the text (derived from Num 23:19?), penned by a redactor to whom the suggestion of a divine change of mind was unacceptable.

The Word Biblical Commentary takes the view that this may be one of the mysteries of God: “Perhaps the paradox expresses teh real truth: He never changes his mind, and yet he does. In other biblical contexts such paradoxes can be gracious: the God who can never forget Zion (Isa 49:15) forgets his people’s sin (Jer 31:34).”

The NET notes (#43) tries to explain that this pertains only to the preceding statement: “This observation marks the preceding statement (v. 28) as an unconditional, unalterable decree. When God makes such a decree he will not alter it or change his mind. This does not mean that God never deviates from his stated intentions or changes his mind. On the contrary, several passages describe him as changing his mind. In fact, his willingness to do so is one of his fundamental divine attributes (see Joel 2:13; Jonah 4:2). For a fuller discussion see R. B. Chisholm, Jr., “Does God Change His Mind?â€? BSac 152 (1995): 387-99.”

I think the NET explanation would be most productive if this came up in a Sunday school class, though I understand this may be stretching the text a bit.

From the AB view, it still remains to explain why the redactor would add this statement without altering verses 11 and 35. Did the redacting process make it easier to add phrases then take away for some reason (people already knew one version of the bible? I need to read up on the particulars of these theories…)?

“Modern investigators were confused overt these insertions about the Davidic covenant. Sometimes the insertions reiteracte this promise that the Davidic kings rule forever, even if they sinned; but sometimes they seemed to be saying just the opposite, that the kings could rule only if they did not sin. … How could the Deuteronomist insert lines that blatantly contradicted each other? Was the covenant conditional or unconditional? If we examine all of the passages that mention the Davidic covenant, we will find that all of the conditional passages spoke of the kings’ holding the throne of Isreal. All of the unconditional passages spoke of the kings’ holding the throne. This petty difference of wording was not so petty to the writer. He had to deal with the fact that David’s family started out ruling the whole united kingdom of Isreal, but they had lost all of it except their own tride of Judah.” [Richard Friedman, Who Wrote the Bible, 141]

But there is still the matter of David’s covenant. According to the Dtr1 history, it was eternal and unconditional. No matter what Manasseh or any other Davidide king did, the throne and the royal city were supposed to be secure forever. The person who was now redoing the history was apparently not willing to cross out that promise as if it had never been there- which is another indication he was not simply commiting pious fraud. How then was he to explain the fall of the kings, temple, and Jerusalem? He did this by drawing his readers’ attention to another covenant: the Mosaic covenant. This covenant that Yahweh had made with the people in the wilderness, according to tradition, was definetely conditional. It required the people to obey God’s commandments or else suffer severe consequences. … This pulled the carpet out from under the Davidic covenant. The fate of the nation ultimately depended on the people, not on the king. The Davidic family’s rule was assured, yes, but if the people’s actions brought about the destruction of the country, then over whom was this family to rule. … Even if unoccupied at the present, there was always the possibility that a descendant of David, a messiah, might come someday and rule justly. The implications for Judaism and Christianity were, of course, tremendous. [Richard Friedman, Who Wrote the Bible, 142-3]

Here’s the New American Bible’s translation of the verse: “If you fear the LORD and worship him, if you are obedient to him and do not rebel against the LORD’S command, if both you and the king who rules you follow the LORD your God—well and good.” The Hebrew text doesn’t have anything comparable to “well and good,” but several translations insert similar phrases to complete the thought of the verse. The verse is a case of aposiopesis, breaking off a sentence before it is completed; it has the “if” part of an “if-then” sentence, but not the “then” part.

I’m having trouble understanding 1 Sam 12:14. I posted my question(s) here. First, the verse seems to be saying that the people will continue to follow the Lord if they obey the Lord, which seems almost tautological (should the future tense be read as a blessing? a prophecy? or what?). Also, what is the significance of mentioning the king only in the second part but not the first? I always thought that under a king the people would fare according to the righteousness of the king, but this verse suggests the opposite, that the king would fare according to the righteousness of the people. . . .

(Sorry to be so far behind the schedule, I should be getting caught up soon. . . .)

As to “prove the armor”: David tried on Saul’s armor, but he couldn’t even walk in it because he hadn’t tried or tested it, meaning he hadn’t been trained in how to use it. So he said to Saul, “I haven’t tested these,” in other words “I don’t know how to use them.”