John Gill Commentary Jeremiah 4:5

"Declare ye in Judah, and publish in Jerusalem; and say, Blow ye the trumpet in the land: cry aloud and say, Assemble yourselves, and let us go into the fortified cities." — Jeremiah 4:5 (ASV)

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 of Judea, and in Jerusalem the metropolis of it, what follows: Declare you in Judah, and publish in Jerusalem, and say

blow you the trumpet in the land; as an alarm of an approaching enemy, and of an invasion by him, and of danger from him; and this was to be done, not in order to gather together, and put themselves in a posture of defence, to meet the enemy, and give him battle; but to get together, that were in the fields, and in country villages, and hide themselves from him:

cry, gather together, and say; or cry with a full mouth, with a loud voice, that all might hear; which shows imminent danger: assemble yourselves and let us go into the defenced cities; such as Jerusalem, and others, where they might think themselves safe and secure; see (Matthew 24:16) .