The following is a passage I contributed to my church's Advent Devotional Book.
plumb line - (n) A) a cord that has at the one end a weight, B) a line directed at the center of gravity of the earth.
The plumb line continues to be one of the simplest tools available to us. Despite its simplicity, it is remarkably accurate, and no matter what resources are joined to create it, the resulting measurements remain the same.
Amos pulls out the plumb line in his prophesy against Israel. Agains the destructive visions God shows Amos, Amos manages to persuade God to relent and have mercy on the people. However given the image of the plumb-line, his interventions go unheeded. The standard, the judgement is true and unfailing.
As Christmas approaches, we see that God did indeed set the plumb-line amongst the people. Through Christ, the one true standard for following God’s will came to be and showed us how He would have us live by living the as our perfect example.