The LORD shall smite thee with madness, and blindness, and astonishment of heart:

Wesley's Notes

28:28 Blindness - Of mind, so that they shall not know what to do: Astonishment - They shall be filled with wonder and horror because of the strangeness and soreness of their calamities.

Jamieson-Fausset-Brown Bible Commentary

28. madness, and blindness, and astonishment of heart-They would be bewildered and paralyzed with terror at the extent of their calamities.

Matthew Henry's Concise Commentary

28:15-44 If we do not keep God's commandments, we not only come short of the blessing promised, but we lay ourselves under the curse, which includes all misery, as the blessing all happiness. Observe the justice of this curse. It is not a curse causeless, or for some light cause. The extent and power of this curse. Wherever the sinner goes, the curse of God follows; wherever he is, it rests upon him. Whatever he has is under a curse. All his enjoyments are made bitter; he cannot take any true comfort in them, for the wrath of God mixes itself with them. Many judgments are here stated, which would be the fruits of the curse, and with which God would punish the people of the Jews, for their apostacy and disobedience. We may observe the fulfilling of these threatenings in their present state. To complete their misery, it is threatened that by these troubles they should be bereaved of all comfort and hope, and left to utter despair. Those who walk by sight, and not by faith, are in danger of losing reason itself, when every thing about them looks frightful.