Albert Barnes Commentary Amos 7:8

"And Jehovah said unto me, Amos, what seest thou? And I said, A plumb-line. Then said the Lord, Behold, I will set a plumb-line in the midst of my people Israel; I will not again pass by them any more;" — Amos 7:8 (ASV)

Amos, what do you see? – He calls the prophet by name, as a familiar friend, known and approved by Him, as He said to Moses, I know you by name (Exodus 33:12, Exodus 33:17). For the Lord knows them that are His. What do you see? (2 Timothy 2:19). God had twice heard the prophet. Two judgments upon His people He had mitigated, not upon their repentance, but on the single intercession of the prophet.

After that, He no longer willed to be entreated. And so He exhibits to Amos a symbol, whose meaning He does not explain until He had pronounced their doom. The plumbline was used in pulling down, as well as in building up. Thus Jeremiah says, The Lord has purposed to destroy the wall of the daughter of Zion; He has stretched out a line; He has not withdrawn His hand from destroying; therefore He made the rampart and wall to lament (Lamentations 2:8). And Isaiah: He shall stretch out upon it the line of wasteness and the stone of emptiness (Isaiah 34:11). And God said of Judah, I will stretch over Jerusalem the line of Samaria and the plummet of the house of Ahab (2 Kings 21:13).

Accordingly God explains the vision, Behold I will set—that is, shortly (literally, am setting)—a plumbline in the midst of My people Israel. The wall, then, is not the emblem of Samaria or of any one city. It is the strength and defense of the whole people, whatever held it together, and held out the enemy. As in the vision to Belshazzar, the word Tekel, He weighed, was explained, You are weighed in the balances and are found wanting (Daniel 5:27), so God here applies the plumbline, at once to convict and to destroy upon conviction.

In this Judgment, as at the Last Day, God would not condemn, without having first made clear the justice of His condemnation. He sets it in the midst of His people, showing that He would make trial of all, one by one, and condemn in proportion to the guilt of each. But the day of grace being past, the sentence was to be final. I will not pass by them anymore—literally, I will not pass over (that is, their transgressions) to them anymore—that is, I will no more forgive them.