John Calvin Commentary Jeremiah 51:38

"They shall roar together like young lions; they shall growl as lions` whelps." — Jeremiah 51:38 (ASV)

Here, by another figure, Jeremiah expresses what he had said about the destruction of Babylon: namely, that in the middle of the slaughter, they would have no strength to resist, and they would, at the same time, perish amidst great confusion. Thus, he anticipates what might have been argued against his prophecy. For the Babylonians had been superior to all other nations; how then could it be that a power so invincible should perish? Though they were as lions, says the Prophet, yet that would be of no use; they will indeed roar, but roaring will be of no service to them. They will roar as lion cubs, but still they will perish.

We now understand, then, the object of this comparison: namely, that the superior power by which the Babylonians had terrified all men would be of no use to them, for nothing would remain for them in their calamity except roaring.