We need to remember that this was originally given to ancient Israel, and the wording applies first of all to the physical people of Israel. However, it contains a spiritual anti-type that we can apply to the end time. In both the type and the antitype, Christ is doing the judging. In the end-time fulfillment, this occurs right before the catastrophe of the Great Tribulation, the time of Jacob's Trouble when things will get really terrible. When the Lord stands on the wall, He says, "Look, this is what you have to be like. You have to be able to stand here next to this plumb line and measure yourself to the vertical to see how upright you really are."
He also says, "I will not pass by . . . any more." This means that judgment is coming, and however this judgment falls, that is it! The first six verses of chapter 7 record two other visions. In those visions, the prophet had said, "Please God, Israel is such a small people. Will you please pass us by this time?" He means, "Will you please have mercy and not punish us?" and both times God replied, "Okay, Amos. Because you have asked Me for this, I will pass by." Now, in this vision of the plumb line, He says, "This time I am going to exact My judgment. I will pass sentence and execute the penalty."
What does He pass sentence on? The "high places of Isaac" indicates idolatry, as do the "sanctuaries of Israel." He says He will "rise with the sword against the house of Jeroboam," meaning that He will wreak a great deal of vengeance upon the leadership of the nation for leading the people away from God and into disaster as they have.
This is very serious. At the time of the end, when God appears with the plumb line, the end it at hand. His judgment will come soon. He is about to react violently, exacting the sentence that He thinks is fair and necessary.
Richard T. Ritenbaugh
The Two Witnesses (Part 5)