John Calvin Commentary Jeremiah 48:4

"Moab is destroyed; her little ones have caused a cry to be heard." — Jeremiah 48:4 (ASV)

The Prophet speaks again generally of the whole country. It is said that the land of Moab was afflicted; not that it was so at that time, but to make the prophecy certain, the prophet speaks of the event as having already taken place. For the prophets, as is well known, speaking in the person of God, relate things still hidden as though they had already been completed.

He says that the little ones of Moab cried out so as to be heard. This is much more emphatic than if he had said that men and women cried out, for children do not quickly perceive what is happening, because their understanding is limited.

Men and women howl when merely threats are announced, but little children are moved only by present evils. Unless they are actually beaten, they are not affected. Even then, they hardly distinguish between some slight evil and death.

Therefore, when the Prophet says that the little ones of Moab were heard in their crying, he means that the severity of its calamity would be extreme, such that little children, as though wise before their time, would perceive the atrocious cruelty of their enemies.