מִ֥י הֶאֱמִ֖ין לִשְׁמֻעָתֵ֑נוּ וּזְר֥וֹעַ יְהוָ֖ה עַל־מִ֥י נִגְלָֽתָה׃
'Who would have believed our report? And to whom hath the arm of the LORD been revealed?
Rashi on Isaiah
Who would have believed our report So will the nations say to one another, Were we to hear from others what we see, it would be unbelievable.
Ibn Ezra on Isaiah
Who hath believed, etc. Then the Non-Israelites shall say, Who would have believed, that it would turn out as we have heard.
Rashi on Isaiah
the arm of the Lord like this, with greatness and glory, to whom was it revealed until now?