John Calvin Commentary Deuteronomy 28:45

"And all these curses shall come upon thee, and shall pursue thee, and overtake thee, till thou be destroyed; because thou hearkenedst not unto the voice of Jehovah thy God, to keep his commandments and his statutes which he commanded thee:" — Deuteronomy 28:45 (ASV)

Moreover, all these curses shall come upon thee. He not only confirms what he has already said but also takes away all hope of relief, since God’s scourges shall not cease until they have repented. He declares that all the curses will come upon them; for although they are not always gathered into a single group, it is still true that God pays the wages of the transgressors of His Law with this multitude of miseries which Moses has recounted.

By the word pursue, he takes away all hope of escape, while to overtake is equivalent to seizing them firmly, until, as it is further said, they are destroyed. In summary, the ungodly by their evasions only cause themselves to accumulate heavier punishments, which will never cease to afflict them until they are destroyed by them.

For this reason, he says that they will be for a sign and a wonder—that is, they will awaken astonishment in all people. For those who are only slightly moved by the common and ordinary judgments of God are compelled, whether they want to or not, to pay attention to these astounding events. Thus, significant punishments, and those deserving special attention, are for a sign and a wonder.

Their ingratitude is also rebuked, as well as their contempt of the Law, because they did not serve God with joyfulness and gladness of heart when He had been so abundantly generous to them. For it is the fault of a corrupt and malignant nature that it cannot be brought to serve God joyfully when He invites us with His generosity. But Moses takes it for granted that, since God will show His favor to the Israelites beforehand, before He proceeds to inflict punishments upon them, they will be guilty of this grievous sin: not allowing themselves to be generously sustained by Him.