Albert Barnes Commentary Nahum 3:18

"Thy shepherds slumber, O king of Assyria; thy nobles are at rest; thy people are scattered upon the mountains, and there is none to gather them." — Nahum 3:18 (ASV)

Your shepherds — that is, those who should counsel for the people’s good and feed them, and “keep watch over their flocks by night,” but are now like their master, the “King of Assyria,” are his shepherds, not the shepherds of the people for whom they do not care. These slumber, at once through listlessness and excess, and now have fallen asleep in death, as the Psalmist says, They have slept their sleep (Psalms 76:6).

The prophet speaks of the future as already past in effect, as it was in the will of God. All “the shepherds of the people,” all those who could shepherd them or hold them together, themselves sleep “the sleep of death.” Their mighty men dwelt in that abiding-place where they will not move or rise—the grave. And so, as Micaiah, in the vision predictive of Ahab’s death, saw all Israel scattered on the hills, as sheep that have not a shepherd (1 Kings 22:17), so the people of the Assyrian monarch will be “scattered on the mountains,” shepherdless, and that irretrievably; no one gathers them.