Deuteronomy 28:46

And they shall be upon thee for a sign and for a wonder, and upon thy seed for ever.

Deuteronomy 28:46 belongs to the chapter that sets the blessings of obedience against the curse that follows disobedience. Those commands were given as God's principles for His people's present and future good. His promises of life and blessing are conditional on doing His judgments and keeping His ordinances and statutes and walking in them.

God placed safeguards before the people to preserve their health and holiness, and obedience was part of His instruction for their journey through the wilderness, while suffering and disease followed transgression of His law. He sent prosperity or adversity according to whether the people obeyed or transgressed His law, which was contained in the ark. This explains why the adult army that left Egypt was refused entrance into the promised land, because they did not wholly follow the Lord, so His purpose toward them was altered.

The curses for disobedience remain upon the people and their descendants forever as a sign and a wonder and a warning. That curse began with Adam's fall, grew heavier after Abel's murder and the Flood, and has continued to increase through succeeding generations as people disobey God, with effects reaching people, animals, trees, and other vegetation.