The words "measuring line" and "plumb line" are metaphors for the standards Yahweh uses to judge people. Alternate translation: "judge Jerusalem using the same measure I used when I judged Samaria and the house of Ahab" (See: [[rc://en/ta/man/translate/figs-metaphor]])
Samaria is the capital city and it represents all the people of the kingdom of Israel. Alternate translation: "against the people of Israel" (See: [[rc://en/ta/man/translate/figs-metonymy]])