In the Bible, a plumb line is a tool used to determine if something (typically a wall or structure) is perfectly vertical or upright. It consists of a weight attached to a string or cord, which, when held against a surface, shows whether that surface is straight or if it deviates from true vertical alignment. Metaphorically, the term "plumb line" is used to symbolize God's standard of righteousness and justice by which He evaluates the moral and spiritual alignment of individuals, nations, or societies. Scriptures like Isaiah 28:17 and Amos 7:8 use the imagery of a plumb line to illustrate God's judgment and the need for alignment with His divine standards. God’s Word is our plumb line for knowing God’s standard by which we are to live.
God calls His people to "be holy, for I am holy" (Leviticus 11:44, 45) and yet, "all have sinned and fall short of the glory of God" (Romans 3:23). While we rely on the Holy Spirit to use God's Word to work in our hearts and for that work to manifest in our actions, we can rest assured that everywhere our lives don't align with God's plumb line we can be "justified by his grace as a gift, through the redemption that is in Christ Jesus" (Romans 3:24). The plumb line of God's standards points us to our need for Christ and His sanctifying work in our lives.
God's Word is as our plumb line, the unerring standard against which we measure our lives. In Isaiah 28:16–17, God establishes justice and righteousness as His foundational principles, declaring them the plumb line by which His people are evaluated. Therefore, as we align ourselves with God's Word, we find clarity and correction, ensuring our lives are upright and truly walking in God’s ways.