The noise of a multitude in the mountains - The prophet here represents himself as hearing the confused tumult of the nations assembling to the standard reared on the mountains Isaiah 13:2. This is a highly beautiful figure - a graphic and vivid representation of the scene before him. Nations are seen to hasten to the elevated banner, and to engage in active preparations for the mighty war. The sound is that of a tumult, an excited multitude hastening to the encampment, and preparing for the conquest of Babylon.
Like as of a great people - Hebrew, ‘The likeness of a great people.’ That is, such a confused and tumultuous sound as attends a great multitude when they collect together.
A tumultuous noise - Hebrew, ‘The voice of the tumultuous noise of the kingdoms of nations gathered together.’
The Lord of hosts - Yahweh, the God of hosts, or armies (note Isaiah 1:9).
Mustereth - Collects; puts in military array. Over all this multitude of nations, hastening with confused sounds and tumult like the noise of the sea, putting themselves in military array, God, unseen, presides, and prepares them for his own great designs. It is not easy to conceive a more sublime image than these mighty hosts of war, unconscious of the hand that directs them, and of the God that presides over them, moving as he wills, and accomplishing his plans.