וְנָטִ֣יתִי עַל־יְרוּשָׁלִַ֗ם אֵ֚ת קָ֣ו שֹֽׁמְר֔וֹן וְאֶת־מִשְׁקֹ֖לֶת בֵּ֣ית אַחְאָ֑ב וּמָחִ֨יתִי אֶת־יְרוּשָׁלִַ֜ם כַּֽאֲשֶׁר־יִמְחֶ֤ה אֶת־הַצַּלַּ֙חַת֙ מָחָ֔ה וְהָפַ֖ךְ עַל־פָּנֶֽיהָ׃
我必用量撒馬利亞的準繩和亞哈家的線鉈來量耶路撒冷；我必擦淨耶路撒冷，如同人擦淨盤子，擦淨後把它倒扣過來。
Rashi
And the plumb line. That is the string to which the builders of a wall tie a lead weight to make the wall straight.2I.e., so that the following rows of bricks or stones will all be directly above one another.
Ralbag
And I will stretch over Jerusalem... : This means that Jerusalem will be given into the hand of an enemy, just as Samaria was given into the hand of the King of Assyria.
Rashi
As one wipes a dish. As one wipes a dish.3Just as one wipes a dish and turns it over so that it should not become soiled or be eaten from any more, so will Yerusholayim be cleaned out of its habitants and then it will destroyed so that it would no longer be habitable.—Radak