In the third of 5 visions given to Amos, God is seen holding a plumb line beside a wall that "had been built using a plumb line" (7:7). Israel was built according to the plumb line. Just 3 months after exiting Egypt (Exodus 19:1-2), God gave Israel His commandments (ch. 20), to be a holy nation (19:6). God established a clear standard: "You must be holy because I, the Lord your God, am holy" (Leviticus 19:2).
Seven hundred years later, God plumb-lined His people "to see if [they were] still straight" (Amos 7:7). And, like the leaning Tower of Pisa, Israel had become seriously tilted. God could not ignore the aberrant angle (v.8). A wall in danger of collapsing had to be toppled (v.9).
God has set His standards for us in His Word. We're to live holy and godly lives (1 Thessalonians 4:7-8; 2 Peter 3:11). One day, we too will be plumb-lined. Yet, God is patient with us, for He wants us to repent (Romans 2:4-6; 2 Peter 3:9,15). But we shouldn't take His patience for granted. For there will come a time when He says, "Look, I am setting a plumb line among my people Israel; I will spare them no longer" (Amos 7:8 NIV).
When God uses His plumb line, will you be found upright or tilted? , K.T. Sim, Our Daily Journey