C. F. Keil and Franz Delitzsch on Deuteronomy 4:25-26

Deu 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. Deu 6:10., Deu 32:15). The apodosis commences with Deu 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 Deu 30:19, had set before them the choice of life and death, and therefore was just in punishing them for their unfaithfulness (cf. Psa 50:6; Psa 51:6). “Prolong days,” as in Exo 20:12.