From The American Vine:

It is when God's judgements are in the earth, that the inhabitants of the world will, if ever, learn righteousness (Isaiah 26:9). May his fatherly chastisements now teach us the salutary lesson by turning the hearts of the disobedient to the wisdom of the just (Luke 1:17). And then, brethren, we shall present to the eyes of men and angels the most sublime spectacle upon earth, that of a whole people bowing themselves before the mercy seat of the Most High in humble acknowledgement of their sinfulness, in earnest suppications for pardon, and with sincere and solemn resolutions of making Him their only trust and their portion forever. Such instances have occurred before and they are recorded for our instruction.

What moral grandeur was there in the voluntary humiliation of proud Nineveh, that exceeding great city of three days' journey, when aroused by the warning voice: Yet forty days and nineveh shall be overthrown! The people of Nineveh, it is said, believed God. They knew His power, that what he said He was able to perform; they knew His justice, that He would by no means acquit the guilty; but they believed also that He was gracious, merciful, and long suffering; and they threw themselves upon his mercy...

God grant that their example not be lost upon us.