John Gill Commentary Amos 7:3

"Jehovah repented concerning this: It shall not be, saith Jehovah." — Amos 7:3 (ASV)

The Lord repented for this
He heard the prayer of the prophet, and at his intercession averted, the threatened judgment; thus the effectual fervent prayer of a righteous man avails much, (James 5:16) ; this is spoken after the manner of men; as men, when they repent of a thing, desist from it, so the Lord desisted from going on with this judgment; he did not change his mind, but changed the dispensations of his providence according to his mind and will: it shall not be, says the Lord
these grasshoppers or locusts, the Assyrian army, shall not at this time destroy the land of Israel: Pul king of Assyria took a sum of money of the king of Israel, and so turned back, and stayed not in the land, (2 Kings 15:19 2 Kings 15:20) .