A Commentary, Critical, Practical, and Explanatory on the Old and New Testaments, by Robert Jamieson, A.R. Fausset and David Brown  at sacred-texts.com
deu 29:1AN EXHORTATION TO OBEDIENCE. (Deu. 29:1-29)
These are the words of the covenant--The discourse of Moses is continued, and the subject of that discourse was Israel's covenant with God, the privileges it conferred, and the obligations it imposed.
beside the covenant which he made with them in Horeb--It was substantially the same; but it was renewed now, in different circumstances. They had violated its conditions. Moses rehearses these, that they might have a better knowledge of its conditions and be more disposed to comply with them.
deu 29:2Moses called unto all Israel, . . . Ye have seen all that the Lord did, &c.--This appeal to the experience of the people, though made generally, was applicable only to that portion of them who had been very young at the period of the Exodus, and who remembered the marvellous transactions that preceded and followed that era. Yet, alas! those wonderful events made no good impression upon them (Deu 29:4). They were strangers to that grace of wisdom which is liberally given to all who ask it; and their insensibility was all the more inexcusable that so many miracles had been performed which might have led to a certain conviction of the presence and the power of God with them. The preservation of their clothes and shoes, the supply of daily food and fresh water--these continued without interruption or diminution during so many years' sojourn in the desert. They were miracles which unmistakably proclaimed the immediate hand of God and were performed for the express purpose of training them to a practical knowledge of, and habitual confidence in, Him. Their experience of this extraordinary goodness and care, together with their remembrance of the brilliant successes by which, with little exertion or loss on their part, God enabled them to acquire the valuable territory on which they stood, is mentioned again to enforce a faithful adherence to the covenant, as the direct and sure means of obtaining its promised blessings.
deu 29:10Ye stand this day all of you before the Lord your God--The whole congregation of Israel, of all ages and conditions, all--young as well as old; menials as well as masters; native Israelites as well as naturalized strangers--all were assembled before the tabernacle to renew the Sinaitic covenant. None of them were allowed to consider themselves as exempt from the terms of that national compact, lest any lapsing into idolatry might prove a root of bitterness, spreading its noxious seed and corrupt influence all around (compare Heb 12:15). It was of the greatest consequence thus to reach the heart and conscience of everyone, for some might delude themselves with the vain idea that by taking the oath (Deu 29:12) by which they engaged themselves in covenant with God, they would surely secure its blessings. Then, even though they would not rigidly adhere to His worship and commands, but would follow the devices and inclinations of their own hearts, yet they would think that He would wink at such liberties and not punish them. It was of the greatest consequence to impress all with the strong and abiding conviction, that while the covenant of grace had special blessings belonging to it, it at the same time had curses in reserve for transgressors, the infliction of which would be as certain, as lasting and severe. This was the advantage contemplated in the law being rehearsed a second time. The picture of a once rich and flourishing region, blasted and doomed in consequence of the sins of its inhabitants, is very striking, and calculated to awaken awe in every reflecting mind. Such is, and long has been, the desolate state of Palestine; and, in looking at its ruined cities, its blasted coast, its naked mountains, its sterile and parched soil--all the sad and unmistakable evidences of a land lying under a curse--numbers of travellers from Europe, America, and the Indies ("strangers from a far country," Deu 29:22) in the present day see that the Lord has executed His threatening. Who can resist the conclusion that it has been inflicted "because the inhabitants had forsaken the covenant of the Lord God of their fathers. . . . and the anger of the Lord was kindled against this land, to bring upon it all the curses that are written in this book"?
deu 29:29The secret things belong unto the Lord--This verse has no apparent connection with the thread of discourse. It is thought to have been said in answer to the looks of astonishment or the words of inquiry as to whether they would be ever so wicked as to deserve such punishments. The recorded history of God's providential dealings towards Israel presents a wonderful combination of "goodness and severity." There is much of it involved in mystery too profound for our limited capacities to fathom; but, from the comprehensive wisdom displayed in those parts which have been made known to us, we are prepared to enter into the full spirit of the apostle's exclamation, "How unsearchable are his judgments" (Rom 11:33).