Amos 7:8

The Lord asked the prophet what he saw, and Amos replied that he saw a plumb line. Then the Lord explained that He was about to test Israel as a builder uses a plumb line. The true standard by which He would judge Israel was undoubtedly the Mosaic Law, the covenant that He had given her by which God measured her uprightness (cf. Exodus 19:6). The Lord further announced that He would not spare the Israelites from His judgment any longer; Amos’ prayers for Israel would not turn away His punishment as earlier (Amos 7:3; Amos 7:6). The nation was so far out of plumb that God would tear it down.