Declare in Judah, and proclaim in Jerusalem, and say, “Blow the trumpet through the land; cry aloud and say, ‘Assemble, and let us go into the fortified cities!’
Jeremiah treats his own people here with more severity, for he saw that they were refractory, and so obstinate in their vices, that they could not by wise counsels be restored to the way of safety. Hence he addresses them here as men wholly irreclaimable, and to whom instruction proved useless.
God's usual method is to warn before he wounds. In these verses, accordingly, God gives notice to the Jews of the general desolation that would shortly be brought upon them by a foreign invasion. This must be declared and published in all the cities of Judah and streets of Jerusalem, that all might hear and fear, and by this loud alarm be either brought to repentance or left inexcusable.
Commenting on Jeremiah 4:5-18
Declare ye in Judah, and publish in Jerusalem, and say,.... Exhortations to repentance being without effect in general, though they might have an influence on some few particular persons, the Lord directs the prophet to lay before the people a view of their destruction as near at hand; who calls upon some persons as a sort of heralds, to publish and declare in the land...