Synopsis of the Books of the Bible, by John Nelson Darby, [1857-62], at sacred-texts.com
The following commentary covers Chapters 28 and 29.
In chapter 28 we have the principles of God's government in the midst of that people, and the immediate consequences of obedience or disobedience-consequences so solemnly fulfilled in the fate of that unhappy people, still beloved for the fathers sakes. The consequences of the violation of the law as a principle of relationship with God, as to the point of a righteousness which was adequate ground of God's acceptance, must not be confounded with the temporary consequences of disobedience under the government of God. It is to these latter that chapter 28 has reference. We may notice for ourselves the deep instruction of Verses 47, 48 (Deu 28:47-48). As to Israel, universal history presents to us the accomplishment of the threats of the chapter.
Chapter 29 is the personal application to the conscience of the people, both collectively and individually, of all that precedes, that there may be no bitter root of sin (compare Heb 12:15, the application of this exhortation to the discipline and the loving care of saints now). Verse 29 (Deu 29:29) requires to be noticed. We find in it the contrast between the consequences thus revealed of obedience and disobedience, and the purposes of God in behalf of the people, notwithstanding their disobedience-purposes which evidently could not be a rule for their conduct. The rule was found in the ordinance of the law. The meaning of this Verse has been so twisted, that it is worth while thus to point out its force. The secret things are the purposes of God with regard to the people, though they should have been disobedient and driven out of the land; but, although they are not the rule of conduct, they are revealed and are of deep interest. In what follows, God begins already to present them to our attention, and surely it becomes us to consider them.
Thus we have, in these chapters, the relationship of the pious Jew with God, grounded upon the accomplishment of the promises made to the fathers, in the present enjoyment of the land; the relationship of the people with God, in view of the curse pronounced upon the violation of the law; the relationship of the people with God, according to the principles of His government, the consequences brought in, either by their obedience or disobedience: and, finally, after the disobedience, and when this has produced its fruit, the designs of God according to His purpose, which nothing could alter.