Charles Ellicott Commentary Deuteronomy 28:20

"Jehovah will send upon thee cursing, discomfiture, and rebuke, in all that thou puttest thy hand unto to do, until thou be destroyed, and until thou perish quickly; because of the evil of thy doings, whereby thou hast forsaken me." — Deuteronomy 28:20 (ASV)

Cursing, vexation, and rebuke. — Deficiency, and anxiety, and failure in every enterprise, would convey the idea, according to another interpretation. There are two views of the derivation of the first of the three words employed. Probably the Authorised Version is right. The three words have each of them the definite article in the original, just as if they were so many diseases. “The curse, and the terror, and the rebuke” of the Almighty are terrible obstacles to any human undertaking.

In all that you set your hand to do. —Literally, in every putting forth of your hand which you make, i.e., in every undertaking. This is the opposite of Deuteronomy 28:8.

You have forsaken me. —Moses and Jehovah are here identified. This is characteristic. The prophets say, “Thus says the Lord.” Moses, whom the Lord knew face to face, sometimes exhorts Israel in His name without any such introduction. (Compare the phrase “to forsake Moses” (literally, apostasy from Moses) in Acts 21:21).