עַל־כֵּ֡ן חָרָה֩ אַף־יְהוָ֨ה בְּעַמּ֜וֹ וַיֵּ֣ט יָד֧וֹ עָלָ֣יו וַיַּכֵּ֗הוּ וַֽיִּרְגְּזוּ֙ הֶֽהָרִ֔ים וַתְּהִ֧י נִבְלָתָ֛ם כַּסּוּחָ֖ה בְּקֶ֣רֶב חוּצ֑וֹת בְּכָל־זֹאת֙ לֹא־שָׁ֣ב אַפּ֔וֹ וְע֖וֹד יָד֥וֹ נְטוּיָֽה׃
Therefore is the anger of the LORD kindled against His people, And He hath stretched forth His hand against them, and hath smitten them, And the hills did tremble, And their carcasses were as refuse in the midst of the streets. For all this His anger is not turned away, But His hand is stretched out still.
Rashi on Isaiah
and the mountains have quaked [This is symbolic of] their kings and their princes.