Albert Barnes Commentary Jeremiah 23:4

"And I will set up shepherds over them, who shall feed them; and they shall fear no more, nor be dismayed, neither shall any be lacking, saith Jehovah." — Jeremiah 23:4 (ASV)

Shepherds - Men like Ezra, Nehemiah, and the Maccabees, raised up especially by God. It is a revocation of the promise made to David (2 Samuel 7:12–16) as far as the earthly throne was concerned.

They shall fear no more ... - The effect of good government will be general security.

Neither shall they be lacking - Not one sheep shall be missing or lost.