Compare with these verses Leviticus 26:33-40, and Deuteronomy 28:64 ff.

When thou shall beget children, and children's children,.... Children and grandchildren, and several ages and generations have passed:

and shalt have remained long in the land; many years and even ages, or have grown old (h) in it: now they were in their infancy, and as such they were about to enter into it; during the times of the judges, they were in their childhood, or youth; in the times of David and Solomon, they were in their manhood; after that, in their decline; and in the times of Jeconiah and his brethren in their old age, when for their sins they were carried captive:

and shall corrupt yourselves, and make a graven image, or the likeness of anything; See Gill on Deuteronomy 25:16.

and shall do evil in the sight of the Lord thy God, to provoke him to anger; that sin of idolatry, that God provoking sin, is chiefly intended.

(h) "inveteraveritis", Montanus: "veteres facti fueritis", Junius & Tremellius, Piscator; "senueritis", Vatablus.

To give emphasis to this warning, Moses holds up the future dispersion of the nation among the heathen as the punishment of apostasy from the Lord.

Deuteronomy 4:25-26

If the Israelites should beget children and children's children, and grow old in the land, and then should make images of God, and do that which was displeasing to God to provoke Him; in that case Moses called upon heaven and earth as witnesses against them, that they should be quickly destroyed out of the land. "Growing old in the land" involved forgetfulness of the former manifestations of grace on the part of the Lord, but not necessarily becoming voluptuous through the enjoyment of the riches of the land, although this might also lead to forgetfulness of God and the manifestations of His grace (cf. Deuteronomy 6:10., Deuteronomy 32:15). The apodosis commences with Deuteronomy 4:26. העיד, with בּ and the accusative, to take or summon as a witness against a person. Heaven and earth do not stand here for the rational beings dwelling in them, but are personified, represented as living, and capable of sensation and speech, and mentioned as witnesses who would raise up against Israel, not to proclaim its guilt, but to bear witness that God, the Lord of heaven and earth, had warned the people, and, as it is described in the parallel passage in Deuteronomy 30:19, had set before them the choice of life and death, and therefore was just in punishing them for their unfaithfulness (cf. Psalm 50:6; Psalm 51:6). "Prolong days," as in Exodus 20:12.

When thou shalt beget children, and children's children, and ye shall have remained long in the land, and shall {q} corrupt yourselves, and make a graven image, or the likeness of any thing, and shall do evil in the sight of the LORD thy God, to provoke him to anger:

(q) Meaning by this all superstition and corruption of the true service of God.

4:24-40 Moses urged the greatness, glory, and goodness of God. Did we consider what a God he is with whom we have to do, we should surely make conscience of our duty to him, and not dare to sin against him. Shall we forsake a merciful God, who will never forsake us, if we are faithful unto him? Whither can we go? Let us be held to our duty by the bonds of love, and prevailed with by the mercies of God to cleave to him. Moses urged God's authority over them, and their obligations to him. In keeping God's commandments they would act wisely for themselves. The fear of the Lord, that is wisdom. Those who enjoy the benefit of Divine light and laws, ought to support their character for wisdom and honour, that God may be glorified thereby. Those who call upon God, shall certainly find him within call, ready to give an answer of peace to every prayer of faith. All these statutes and judgments of the Divine law are just and righteous, above the statutes and judgments of any of the nations. What they saw at mount Sinai, gave an earnest of the day of judgment, in which the Lord Jesus shall be revealed in flaming fire. They must also remember what they heard at mount Sinai. God manifests himself in the works of the creation, without speech or language, yet their voice is heard, Ps 19:1,3; but to Israel he made himself known by speech and language, condescending to their weakness. The rise of this nation was quite different from the origin of all other nations. See the reasons of free grace; we are not beloved for our own sakes, but for Christ's sake. Moses urged the certain benefit and advantage of obedience. This argument he had begun with, ver. 1, That ye may live, and go in and possess the land; and this he concludes with, ver. 40, That it may go well with thee, and with thy children after thee. He reminds them that their prosperity would depend upon their piety. Apostacy from God would undoubtedly be the ruin of their nation. He foresees their revolt from God to idols. Those, and those only, shall find God to their comfort, who seek him with all their heart. Afflictions engage and quicken us to seek God; and, by the grace of God working with them, many are thus brought back to their right mind. When these things are come upon thee, turn to the Lord thy God, for thou seest what comes of turning from him. Let all the arguments be laid together, and then say, if religion has not reason on its side. None cast off the government of their God, but those who first abandon the understanding of a man.