Jeremiah 18:9

And at what instant I shall speak concerning a nation, and concerning a kingdom, to build and to plant it;

At a given moment God may speak concerning a nation and concerning a kingdom to build it and to plant it, which is to announce blessing and prosperity for it. He may thus declare his intent to build up and plant a nation or kingdom. Nations no less than individuals are under His power and authority, and He governs them as a potter shapes clay in his hands, yet their response to Him affects how He deals with them.

The good so promised is conditional on the nation's course and obedience, not absolute. If it does evil in His sight and refuses to obey His voice, He may withdraw and withhold the good He intended and promised for it. Past guilt does not fix a nation's fate, nor does past virtue secure it, for the sins of earlier generations do not condemn a nation that turns from sin, and the virtues of its fathers do not protect descendants who choose evil. Conversely, when those under threatened judgment turn from evil, He may likewise relent from the evil He had purposed.

He has power both to build up and to bring down, and His dealings remain on the side of righteousness and truth. In its setting Judah was warned to return to good ways, but its people refused and opposed the prophet. The announcement therefore stands as a call to repent and make one's ways and doings right, for God warns and pleads for men to turn from evil and do what is right. Those who follow Him receive blessing, while those who persist in their own ways prove unfaithful and cannot be blessed.