וְהָיָ֣ה ׀ בַּיּ֣וֹם הַה֗וּא לֹֽא־יוֹסִ֨יף ע֜וֹד שְׁאָ֤ר יִשְׂרָאֵל֙ וּפְלֵיטַ֣ת בֵּֽית־יַעֲקֹ֔ב לְהִשָּׁעֵ֖ן עַל־מַכֵּ֑הוּ וְנִשְׁעַ֗ן עַל־יְהוָ֛ה קְד֥וֹשׁ יִשְׂרָאֵ֖ל בֶּאֱמֶֽת׃
Rashi on Isaiah
to lean on him that smote them [i.e.,] to lean on the kings of Egypt, who were the first to oppress them.
Ibn Ezra on Isaiah
That smote them, the Assyrians. This verse shows, that many of the men of Judah conspired against their king.