John Gill Commentary Deuteronomy 28:37

"And thou shalt become an astonishment, a proverb, and a byword, among all the peoples whither Jehovah shall lead thee away." — Deuteronomy 28:37 (ASV)

And you will become an astonishment
To neighbouring nations, that will hear of their overthrow and captivity, and that will see the miserable condition they are brought into:

a proverb and a byword among all nations where the Lord will lead
you;
both for the wickedness committed by them, and for the ill usage of them by the nations among whom they should be, as they were in the Babylonish captivity; see (Jeremiah 24:9) ; and now are, it being common to say, ``do you think I am a Jew?'' or, ``none but a Jew would have done such a thing.''