The Lord repented for this - God is said to "repent, to have strong compassion upon" or "over" evil, which He has either inflicted Deuteronomy 32:36; 1-Chronicles 21:15, or has said that He would inflict Exodus 32:12; Joel 2:13; Jonah 3:10; Jeremiah 18:8, and which, upon repentance or prayer, He suspends or checks. Here, Amos does not intercede until after the judgment had been, in part, inflicted. He prayed, when in vision the locust "had made an end of eating the grass of the land," and when "the fire had eaten up a part." Nor, until Israel had suffered what these visions foretold, was he "small," either in his own or in human sight, or in relation to his general condition. The "this" then, "of which God repented" and said, "it shall not be," is that further undefined evil, which His first infliction threatened. Evil and decay do not die out, but destroy. Oppression does not weary itself out, but increases. Visitations of God are tokens of His displeasure, and, in the order of His justice, rest on the sinner. Pul and Tiglath-pileser, when they came with their armies on Israel, were instruments of God's chastening. According to the ways of God's justice, or of man's ambition, the evil now begun, would have continued, but that God, at the prayer of the prophet, said, "Hitherto shalt thou come, and no further" Job 38:11.

The Lord repented - Changed his purpose of destroying them by the locusts. See Amos 7:6.

The LORD (c) repented for this: It shall not be, saith the LORD.
(c) That is, stopped this plague at my prayer.

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, saith 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.

repented for this--that is, of this. The change was not in the mind of God (Numbers 2:19; James 1:17), but in the effect outwardly. God unchangeably does what is just; it is just that He should hear intercessory prayer (James 5:16-18), as it would have been just for Him to have let judgment take its course at once on the guilty nation, but for the prayer of one or two righteous men in it (compare Genesis 18:23-33; 1-Samuel 15:11; Jeremiah 42:10). The repentance of the sinner, and God's regard to His own attributes of mercy and covenanted love, also cause God outwardly to deal with him as if he repented (Jonah 3:10), whereas the change in outward dealing is in strictest harmony with God's own unchangeableness.
It shall not be--Israel's utter overthrow now. Pul was influenced by God to accept money and withdraw from Israel.

Repented - This is spoken after the manner of men.