Thus he showed me; and behold the Lord stood upon a wall made by a Plumb Line, with a Plumb Line in his hand. And the Lord said unto me, Amos, what seeth thou? And I said, A Plumb Line. Then the Lord said, Behold I will set a Plumb Line in the midst of my people Israel. I will not again pass by them anymore.

Amos, chapter vii, verses 7, 8